TAGAP stands for "The Apocalyptic Game About Penguins." It's actually a cleverly disguised way for the creator to be against animal testing. See, genetically enhanced penguins turn on humans, and want to destroy everything and everyone.
TAGAP is a 2D sidescroller, but with 3D acceleration, which means it looks awesome. The plot is basically what I said above. You're a penguin named Pablo who broke out, and now wants to destroy his creators. The controls are really good and smooth, the gameplay runs smoothly, and everything is basically fun. There's a fairly good diversity of weapons, such as an uzi, dual uzis, rocket launcher, and a few more. The levels get a little old; it's got a Halo-style theme: blast through everything and get to where you're going. It is challenging, don't doubt.
The enemies are a bit annoying. The AI is not incredible, and the spawns are neverending. This means that if you stand at one end of a hallway, there will be a neverending stream of enemy penguins coming down to defeat you. And when you have limited ammo, this can be annoying sometimes.
Overall, it's a pretty good game. There are a few downsides, one being the install size. My install is 130mb, which I call big. The other would be the system requirements. It does look amazing, but this takes a toll. The site calls for 1000+ MHz processor, 256mb RAM, OpenGL, and I believe I saw that DirectX is also required. Is all this bad? Naw. It can run on a pretty low system, but it's not "lightweight."
Oh, did I mention it's portable? According to The Portable Freeware Collection, extract the game to your flash drive, and beat penguins on the go.
Also, be sure to check out TAGAP2 as well if you liked TAGAP