Cube in an opensource shooter designed to run on systems with lower resources availabe. Cube uses opensource content, as well as a few quake II models, in its game portion. Cube supports both single and multiplayer. Maps can be of both large size and hold a large number of computer AI's. Cube has a large multiplayer community, and maps can be edited in real time cooperatively. There are several single and multiplayer mapping projects underway, as well as model packs and total conversions.
Here's the first Grenade Launcher for AC. It gives a whole new feeling to grenades :) You can use this weapons in other games too, but please stick to the readme, which I included in the download :)