[QUOTE=BluePhaze] Just a matter of opinion, take the types of games you like to play and think of the things you wish they did, or that bug you, and use that.[/QUOTE]
This is a great to come up with something new to work with, I do it all the time.
People will have more fun doing things they're familiar with anyway. That way when they play a game new to them they won't have a whole lot of learning to do.
You could always try and "innovate" if you want. But the best way to do that would be to play what's already out and create what's not. But chances are somebody somewhere has created that mechanic anyway.