I bought this game from pogo to go, and enjoyed the hell out of it. it's called Alien Shooter, and it's basically an isometric arcade-style doom-ish game. It's a boatload of fun though, and I'm really looking forward to the sequel which is currently in the works.
If you're a fan of 2-D games, as I am, you'll love it, i promise.
They've also made a few addons for the original Alien Shooter too, but i haven't tried those..
Alien Shooter: (download the demo at the bottom of the page) http://www.sigma-team.net/runcms/modules/mydownloads/viewcat.php?cid=8
and the new Alien Shooter 2: http://www.sigma-team.net/runcms/modules/sections/index.php?op=viewarticle&artid=3
These guys also did a very awesome version of "Breakout" called "Riccochet". It's by far the best breakout clone i've ever played.