Shedinja is a dual Bug/Ghost-type, and it has the unique ability Wonder Guard, which only allows it to be damaged by super-effective moves. It remains vulnerable to status and weather conditions, however. It also only has 1 HP, making it a very, very risky Pokémon to use in a Nuzlocke.
Shedinja is available in all Hoenn and Kalos-based games, as well as HeartGold and SoulSilver.
Completed analyses of Shedinja so far: