Metagun sticks you in trenchcoat and fedora and asks that you navigate a 2D platform maze. Your progress, however, will be thwarted by various destructible obstacles. Except you can't directly destroy them. You can only fire little people out of your gun and these little people then start shooting at you. Entice them to shoot towards an object you want destroyed, then dodge out of the way, and you'll be able to clear a path.
It works because it demands you rethink the way you'd approach similar puzzles in any other 2D platformer. It also demands you're pretty nimble on the keys, since those little people will keep trying to shoot you well after they destroyed that obstacle you needed them for. Things can get very hectic very quickly if you're not careful.
My favourite bit though is the health mechanic where your fedora is your shield.