Blitzle is only available on Route 3 in both games, and has an encounter rate of 20%. Zebstrika is only available on Route 7 in both games, and also has an encounter rate of 20%.
The first of the few, and very rare, Electric-types found in Black and White! Very useful from the get-go, and with an awesome base-60 power STAB move available as early as level 11, Blitzle is really strong shortly after being caught and can hold its own for a good chunk of the game. Being Electric-typed, it also does not fear very many opponents after evolution, at least in the mid-game; later on, the prowess of this line sadly wears out, but is indeed still capable of proving itself useful even just for the typing alone. Starting from after Elesa, Zebstrika is also a fantastic lead, thanks to Volt Switch access and having high Speed and only one weakness. Despite being a bit of a one-trick pony (or zebra) with a fairly barren movepool, it is a good choice for inexperienced players and unlikely to disappoint more experienced ones, for well over half of the game; after that, though, Zebstrika usage is only recommended to the more experienced, as beginners are unlikely to make the most out of the limited options they have.
N (Nacrene City): Pidove and Tympole are easy to beat, but Timburr requires more care: it has Bide and Blitzle can only 3HKO it with Shock Wave, so if Bide only lasts two turns, Blitzle or another Pokémon will be dead. Do not use Thunder Wave against it, it will only spam Guts-boosted Low Kick and that will not be fun for any team member.
Gym #2 - Lenora (Nacrene City, Normal-type): Absolutely no business fighting either of them, as Blitzle's Defense is ridiculous for something as broken as STAB Take Down, or even worse, KO-boosted Retaliate. Do not use Blitzle.
Gym #3 - Burgh (Castelia City, Bug-type): While spamming Flame Charge may sound like a good idea, it really is not, at least against Whirlipede: it has very good Defense and will only fall to three or four hits, plus it might put Blitzle in serious danger with Poison Tail. The Eviolite helps, but it is likely that it will poison at least once, and Blitzle will have to be healed to continue. Dwebble is better: Blitzle should Flame Charge it once to get the Speed boost, and then KO with Spark if it knows the move, or Shock Wave otherwise. Bear in mind that Dwebble could Sand-Attack and, while this is not a huge problem for Dwebble itself, especially with Shock Wave in Blitzle's roster, it will be if Blitzle stays in to fight Leavanny, only to miss Flame Charge afterwards. As for Leavanny itself, both its Razor Leaf and Blitzle's Flame Charge are 2HKOs, which is why the Speed boost is important: without it, Blitzle would never win the matchup.
Bianca (Castelia City): Do not fight Herdier, it is as dangerous as Lenora's. The elemental monkeys are easy instead, and the starters are doable, respectively with Shock Wave or Spark for Pignite and Dewott, and Flame Charge for Servine; Servine can only 3HKO with Leaf Tornado, providing that Blitzle is holding the Eviolite (which should always be the default, since this line is frail). Munna should not pose problems.
Cheren (Route 4): Pidove is easy and so are the elemental monkeys, as stated in the Bianca fight above. The same principles also apply for the starters: exploit type effectiveness and/or STAB. Pignite's Arm Thrust may actually make Zebstrika want another counter for it, as two consecutive turns of 4-5 hits each will off even Eviolite Blitzle, however unlikely this happenstance may be; Liepard, while less powerful than Bianca's Herdier, is still an evolved Pokémon that can dent Blitzle's HP considerably, but Spark can 3HKO it and it has the welcome plus of a high paralysis chance. Once again, this is only possible with the Eviolite, as Blitzle has no other way of beating it.
N (Nimbasa City): If Zebstrika is already evolved, it only really needs to avoid Sandile, for obvious reasons; the rest will fall easily to Spark. If Blitzle has not yet evolved, this fight is a deadly mix of dangers: Scraggy's Brick Break, Darumaka's Fire Punch and Sigilyph's general over-the-top stats for this point in the game, as well as higher Speed than Blitzle's, make this fight impossible for the frail zebra, and dangerous even with the Eviolite attached, though in this case it may be able to take down a Pokémon before withdrawing. Sigilyph can be the one that Blitzle takes down only if Spark achieves paralysis, otherwise only Scraggy and Darumaka are possible, and not without risking critical hits, which can seriously endanger Blitzle.
Gym #4 - Elesa (Nimbasa City, Electric-type): Zebstrika has the upper hand over both Emolga, hitting them for neutral damage with Spark and suffering low damage from their own attacks, though it is possible that their Static will paralyse the zebra and impair its fighting capabilities against Elesa's own. Otherwise, Elesa's Zebstrika is a mirror match, which Zebstrika can win if it learns Return before the fight. Zebstrika can also play a support role, setting up Light Screen for its teammates to take less damage from Volt Switch, in case Zebstrika needs to switch out against Elesa's own. If Zebstrika has Return, it can use it against the Emolga as well, as it should be more powerful than Spark and it does not carry the risk of triggering the opposing Zebstrika's ability in the event that they switch out (unlikely, as they cannot use Volt Switch against Zebstrika).
Cheren (Route 5): Zebstrika's now-evolved status makes the whole fight a whole lot easier. It can simply use Spark against everything that does not resist it, and use Flame Charge for the Grass-types.
Gym #5 - Clay (Driftveil City, Ground-type): Not a chance. Keep Zebstrika out of this fight, it has absolutely no business entering the battlefield; even Flame Charge is pitifully weak against Excadrill's Bulldoze.
Bianca (Driftveil City): Again, nothing troublesome for a Zebstrika, as even Herdier's Take Down is far less hurtful now. Spark can be used against everything except the Grass-types, which should be dealt with through Flame Charge, or potentially Return. Zebstrika will need to negate Herdier's Intimidate in order to keep a slew of 3HKOs going; otherwise, Musharna will take three Sparks and its Psybeams will eventually kill Zebstrika, or at least wear it down just enough to make more healing items necessary.
N (Chargestone Cave): Apart from Boldore, which has high Defense and is probably best KOed by Shock Wave, the rest of his team is weak to Fire, which suits Zebstrika's Flame Charge perfectly. Return may actually do more damage if at maximum happiness, but only to Joltik, as the other two Pokémon resist it.
Cheren (Route 7): More Spark spam against everything, except Simisage; its Seed Bomb is almost a 2HKO against Zebstrika, but that can be remedied with Flame Charge supported by the Expert Belt, which will 2HKO in turn. The rest is as easy as ever; Zebstrika should be able to solo Cheren's team without problems.
Gym #7 - Brycen (Icirrus City, Ice-type): Zebstrika can score more easy winnings with Flame Charge or Spark. Vanillish and Cryogonal are not problematic, as they are physically frail and Zebstrika is faster than them; with the Expert Belt, Vanillish can be 2HKOed by Flame Charge, and Cryogonal is a close possible OHKO but not quite. However, Zebstrika can also take a Frost Breath from each. Beartic is another story, though: it will only fall to three or more of Zebstrika's hits, and it can retaliate with Icicle Crash, which is a clean 2HKO or an OHKO if it becomes a critical hit. Avoid using Zebstrika against Brycen's ace.
Bianca (Route 8): Stoutland is the lead and main danger of this team, but the others are not weak either. Stoutland's Work Up and Retaliate make it very dangerous, and it can take several hits from the zebra, especially after Intimidate is factored in. Zebstrika needs to either Volt Switch to a teammate, or leave the fight to that from the get-go, because it will not survive more than a hit or two, and starting at a single Work Up, Stoutland can OHKO with a critical hit. Musharna can be 3HKOed with Spark or Thunderbolt, but also puts a severe dent in Zebstrika's health with two Psybeams. The elemental monkeys except Simisage can be fought relatively easily; Simisage is 2HKOed once again by Flame Charge supported by the Expert Belt. Samurott is the "easy" starter, but also the one that can kill with a single critical Revenge after living a hit; Thunder Wave is better to start off the fight. Serperior lives up to three hits without Coil and even more if it starts using the move, so another Pokémon must deal with it. Emboar is about average; Zebstrika is just heavy enough to minimise damage from Heat Crash, and its next best move is Take Down, a mere 3HKO like Zebstrika's Thunderbolt.
Gym #8 - Iris/Drayden (Opelucid City, Dragon-type): No. Everything in this gym resist Electric moves and can use any single turn given to them to set up Dragon Dance and then sweep the whole team off its feet. Keep away; Zebstrika would only provide them with setup fodder.
Cheren (Route 10): Grass-types are best avoided due to how powerful they have become, Serperior especially; Simisage can still be 2HKOed by Expert Belt-boosted Flame Charge. Water-types are the easy ones; Simisear is about evenly matched but Emboar is better left to a more fitting counter, as its Flamethrower can easily wreck Zebstrika. Unfezant and Liepard can be defeated easily instead.
Elite Four Shauntal (Pokémon League, Ghost-type): Stalling Cofagrigus is possible, but Zebstrika will need healing due to Toxic and Wild Charge recoil; Jellicent is OHKOed by Wild Charge, but nothing less powerful can do the trick, while Golurk is far too strong and immune to Zebstrika's STAB. Do not fight Chandelure, either: it will not die to any less than three of Zebstrika's hits and its Fire Blast can kill from full health.
Elite Four Marshal (Pokémon League, Fighting-type): No Pokémon except Mienshao is within Zebstrika's league. Marshal's Pokémon have a lot of bulk, and the powerful moves they have spell death and bloodshed for the frail zebra. Sawk might be 2HKOed by Wild Charge, if two high enough damage rolls occur, but its Stone Edge crits easily and the recoil piles up on its damage. Mienshao is a glass cannon, instead, so it can be two-shot by Thunderbolt and Wild Charge used in succession, keeping in mind that its Jump Kick is really strong and can chip off up to around 80% of Zebstrika's health. Depending on how much Thunderbolt does, Zebstrika may opt for withdrawing instead, through Volt Switch. If Zebstrika has a Ghost-type to switch to, and Mienshao does use Jump Kick, it will end itself, sparing Zebstrika's team the trouble.
Elite Four Grimsley (Pokémon League, Dark-type): Scrafty can be defeated; Zebstrika will not damage it a lot, but neither will it. Likewise, Liepard should be easy, as it is frailer and less powerful than the zebra. For the other two, a better matchup is needed: Bisharp will not die easily to anything Zebstrika has and the reverse is very true, while Krookodile's type advantage is enough to scare Zebstrika away.
Elite Four Caitlin (Pokémon League, Psychic-type): Sigilyph is the only straightforward fight here, OHKOed by Wild Charge supported by the Expert Belt, while Gothitelle and Reuniclus are far stronger; both of them can 2HKO Zebstrika with Psychic, and Zebstrika cannot do anything but 3HKO them at best. For Gothitelle, however, Zebstrika can try baiting Thunderbolt with a Pokémon weak to Electric moves, then switch in and hope that the prediction is correct; it will only work for Lightning Rod specimens, though, as Motor Drive ones will not do anything at all with the Speed boost if they cannot OHKO next (and they will not). The same can be done with Musharna's Charge Beam; Lightning Rod makes it somewhat likely that Zebstrika may 2HKO Reuniclus and Gothitelle with Thunderbolt, but once again it will not be able to fight both, and the 2HKO is still uncertain despite the Special Attack boost.
Reshiram/Zekrom (N's Castle): Again, do not do this. Neither legendary will be afraid of Zebstrika's resisted Electric moves, especially Zekrom, while their own moves can make the frail zebra crumble to dust in the blink of an eye. A more suitable Pokémon is needed for this fight.
N (N's Castle): Zebstrika should never fight Reshiram or Zekrom, two major threats to its safety. Carracosta has Sturdy, but Zebstrika can take a non-critical Stone Edge and 2HKO it with Thunderbolt. Klinklang is not too powerful, but after a Metal Sound, Hyper Beam starts to really hurt; Zebstrika should start with Thunderbolt, but be ready to Volt Switch out if and when needed. Zoroark, once unmasked, will fall to any two hits off Zebstrika's STABs and can at best 3HKO with Night Slash, though not counting critical hits, which can indeed happen. Archeops is OHKOed by both Thunderbolt and Wild Charge, and will usually be outsped by Zebstrika, though Speed-lowering natures should run calculations to verify this is indeed the case. Keep away from Vanilluxe and its Blizzard.
Ghetsis (N's Castle): Only Cofagrigus can be beaten with three Thunderbolts, and only because it is slow, as its Shadow Ball comes very close to a 2HKO against Zebstrika. Bisharp might not 2HKO with Night Slash either, if Zebstrika's Defense is good enough; Thunderbolt will 3HKO it... except its Metal Burst will kill Zebstrika long before that happens, so there is no way it can be fought without having Zebstrika die against it. Bouffalant has Earthquake, and the rest either resists or is immune to Electric moves as well as having more than enough raw power to destroy Zebstrika completely. Unless forced to, do not tread here.
Post-Game: At long last, Zebstrika gains access to Overheat, but its power has long since started to fall short. There are better Pokémon to use by now.
Blitzle's initial moveset consists of Quick Attack, Tail Whip and Charge. It learns its first STAB move at level 11, which is Shock Wave, incredibly powerful for this point in the game; Thunder Wave comes at 15 instead, and is a good support move in general, though Blitzle will probably only use that for catching help. At level 18, it learns Flame Charge, which complements its coverage nicely and is very useful in the short term, especially against Burgh. Then, it gets Pursuit at 22, another situationally useful move, though it will likely always deal less damage than Spark, which comes at 25; the AI in the game tends to switch approximately never at all. After evolving, Zebstrika gets Stomp at 31, which is not very useful, and then Discharge at 36; the usefulness of this move depends on Zebstrika's stats: it may or may not do more damage than Spark, depending on IVs and nature. At 42, the line learns Agility, though Thunder Wave is better and neither of them is usually needed. The upgrade to Spark comes at level 47 instead, in the form of Wild Charge. Lastly, if Zebstrika ever gets that far, it gains access to Thrash at level 53, though most of the time, it will not be worth learning due to Return being a much less risky and only marginally less powerful option.
A useful TM option is of course Thunderbolt, for specially oriented zebras, and also Volt Switch in general, even if Zebstrika already has physical STAB: it will help Zebstrika deal some damage before it ducks from opponents it cannot fight. Flame Charge and Wild Charge are both available via TM too, so Zebstrika can learn or relearn them at will. Overheat is plain amazing, but sadly unavailable until the postgame. Defensive options include Light Screen, for more durable zebras, and not much more. If Zebstrika is pressed for higher power moves, it can be taught Return, which Zebstrika's barren movepool actually appreciates.
Pokémon that are good against Ground-types: Zebstrika's main concern is getting proper team coverage against Ground-types, since its moves can do nothing against them. Grass-types are usually best for this role, as they sport a resistance as well as super effective STAB; Water-types can work well, too, though Flying-types are usually discouraged due to how commonly Ground-types sport Rock moves.
Physical tanks: Neither of Zebstrika's defensive stats is great, but its Defense will most often be glaringly lacking, since Unova has a number of physically-oriented bosses and Ground-type moves are usually physical in nature. A physical wall is also necessary on the team.
Special tanks: Zebstrika's low Special Defense also needs proper coverage. There are several readily available options, and most Pokémon with good Special Defense are not weak to Ground, which is good given Zebstrika's lone weakness. A Pokémon with a Ground resistance or immunity works even better.
Minimum stats are calculated with 0 EVs, IVs of 0, and a hindering nature, if applicable.
Maximum stats are calculated with 252 EVs, IVs of 31, and a helpful nature, if applicable.
Blitzle Line Ratings
What Nature do I want? Lonely or Naughty for maximum attacking power; Mild and Rash also work well in the short term, though Attack boosts are better than Special Attack boosts starting from Spark level onwards. Whatever lowers either attacking stat is undesirable, especially if it lowers Attack. Speed drops are not too bad, except against Archeops.
Which Ability do I want? Neither is particularly useful as Zebstrika is a largely physical Pokémon, though if anything, more Speed is definitely not on its wishlist. Thus, Lightning Rod will usually help more than Motor Drive, but most of the time they will be equivalent.
At what point in the game should I be evolved? Definitely before Elesa, and it would help in general to have a Zebstrika before setting foot in Nimbasa City; Blitzle alone is fairly frail, and even the Eviolite does not help it much.
How good is the Blitzle line in a Nuzlocke? Very good in the beginning, and fairly good in the mid-game. Towards the end, it tends to lose some of its steam in boss fights, though mostly due to how late Wild Charge is and its measly movepool, as well as its mediocre defensive stats; the last, dragon-packed stretch is a nightmare for this line.
Resistances: Flying, Steel
Immunities: Electric (Lightning Rod or Motor Drive)
Neutralities: Normal, Fighting, Poison, Rock, Bug, Ghost, Fire, Water, Grass, Psychic, Ice, Dragon, Dark