Anyone here heard of Facewound? It was a game that the creator of Garry's Mod made (along with a few others). I always wanted to play it and it seems he released the latest version, which is a few years old, on his site. (He stopped working on it and started working on his hl2 mod, gmod/garrys mod).
http://www.garry.tv/?p=512
Game is very easy to mod. It comes with a map editor.
Type of game it is is a side-scrolling shooter. It uses a lot of cool graphical effects.

Oh yeah, Ive made a few retarded maps of that game (Lol like making attack choppers shoot EVERWHERE all the time, like 50 of em at once in all directions)