4. Bug - Doug Jones
Granted, there are no assurances that Bug will even appear in Guardians of the Galaxy, but if James Gunn has his head screwed on right, he will ensure to include the antennae-clad being, who can communicate with other similar creatures in the same was as a regular insect, but is also an extremely capable tactician and soldier. In much the same way as Andy Serkis has cornered the market on performance-capture, Doug Jones is Hollywood's go-to-guy for complex prosthetic work, not only for his seemingly masochistic penchant for spending hours a day in a make-up chair, but the subtle inflexions he infuses into the characters through his inventive mannerisms and unique voice. One need only look as far as his brilliant work on Guillermo Del Toro's Hellboy films and also Pan's Labyrinth to see that he is the only guy even worth trying to cast as Bug.