Gunnihilation is a stripped down 2D run and gun platformer. No tricks, just you verse increasingly large numbers of dudes (and dudes inside robots) who don't like you very much using raw fire-power and high manoeuvrability.
Blast them away with your Machine gun/Shotgun... or if things get hairy turn to the power of your anger and unleash a Minigun/Rocket launcher and shred them into little bits.