Not really a small thing, and not really model related (well, a bit):
In ODST, Buck is voiced by Nathan Fillion, and his model is based off of him. Now I'm sure most people noticed this, but what some people DON'T know is that Dutch is voiced by Adam Baldwin (who plays Jayne Cobb) and Mickey is voiced by Alan Tudyk (who plays Wash). AS an avid Firefly fan, this fact alone mad the game awesome