Slugma is available on Routes 16, 17 and 18 in all Johto-based games. In Heart Gold and Soul Silver, it is also available as an Egg from Primo in Violet City. In all Hoenn-based games, it is available on the Fiery Path and, in Emerald only, on Route 113 as well. In all Kalos-based games, it is available on Route 13 by smashing rocks.
Completed analyses of the Slugma line so far: