Sometimes a premise is all you need. Build your own robot from a big pile of parts, then have it fight someone else's robot. Sold? Good. Check out the Rawbots video below.
This is from indie dev Alex Rozgo, and is clearly a little more complicated than just fighting the robots. The building system looks really interesting, and enormously complex. It's certainly caught our eye.
It'll be interesting to see how it is to use, but unfortunately finding out more details about the game is tricky, since it apparently only has a Facebook page at this point. Indies! You can't skimp on a proper info page! Just the mad cavalcade of a Facebook timeline is going to lose you interest and therefore customers.