The Buffy and Angel ones are from the PALz series by Palisades Toys, who also did some X-Files characters. They would package one character with lots of accessories, including several alternate body parts in order to give them changes of clothes.
I'd love some Firefly minimates, as well as Heroes, Doctor Who, Stargate (SG-1 and Atlantis), Indiana Jones, and Star Wars. Anything that inspires its own large scale fan conventions is probably a safe bet for TPTB. The Rocky and Back to the Future ones kind of threw me for a loop, so anything goes I guess.