If you've never played TAGAP - that's "The Apocalyptic Game About Penguins"- yet, you're seriously missing out. It's an extremely unique, fun, addicting sidescroller starring -you guessed it: Penguins. Words really don't give it justice. I mean, there are a ton of different guns, baddies, and levels....but that doesn't really capture just how fun this game is. Everything about it is just relaxing: the graphics, the soundtrack, the sound effects, and even the idea of just mowing down a line of zombie penguins with a minigun. It's challenging yet relaxing, intense yet subtle. It is the most possible fun you can have involving penguins without physically owning a penguin.
The best part? Both TAGAP and TAGAP 2 are free. So please, go, download them, give them a try. TAGAP 2 even has co-op mode so you can play with a friend.