Catdammit is a free game about a "hobo cat with a chainsaw". You can play it in your browser here, or watch a video below. I recommend the former. Made entirely in the free version of Unity, this certainly shows what you can do with a free game engine, a brain, and some cheap dreams of an arcade world in which a cat destroys everything with a chainsaw. Worth playing, if just for the way trees dance happily until you chop them down.