I really like the concept of Headhunters, how cool would it be to play a game featuring them?
Being a super-soldier who charges in and kills everything in the face is fun and all, but one of the things I liked about ODST is that it really helped to be stealthy. Wiping out half the covenant before they realize you're there is rather enjoyable. Maybe some elements of Splinter Cell conviction in there?
What do you guys think?