I like Shining Pokémon (both the kind with "Shining" in their name and the ones denoted with a star, don't know why people call them "Pokémon star"... it annoys me for some reason, but chances are, people are probably also annoyed with others calling them "Shining"...). Their attacks have cool effects, but they are either hard to use or very situational. I like making Shining fakes a lot, but I have to use existing artwork and apply effects to it, rather than draw my own.
The crystal-types have also intrigued me, since they are both in the TV show and in the TCG. If they are in both of those places, why aren't they in the GB game? Oh well. I like the idea of a monster being able to turn into an unusual type. Crystal Celebi and Ho-oh are very cool.