I actually wouldn’t call myself very active in any of these fandoms these days. I just greatly enjoy the titles in question. Though I have gone as far as having fan-characters for a select few of them.
Aliens vs Predator
Digimon (The first three shows and the monster designs.)
Fallout (3 and New Vegas. Can’t get into the gameplay of the others.)
My Little Pony: Friendship is Magic
Panty & Stocking with Garterbelt
Pokemon (The games exclusively.)
Transformers (Beast Wars, Animated, War for Cybertron, and Prime. I really can’t get into the others, especially the Japanese stuff.)