ehehehe.......
halo :>
:<
Seriously though, I'm really inspired by movies and more importantly, video game characters.
The great thing about the video game ones are that there are usually great renders that I can work off of.
Usually, the designs of large franchises are leagues above my own, so the heads turn out nicer looking and better proportions too. Additionally, there would be a fan base which would make selling the head a lot easier.
Novelty stuff, really
Right now, I'm inspired by crysis, which has an excellent model to study, and I hope to be inspired by the suits in the GI joe movie (hopefully, they aren't too detailed or too reflective)