Ultimate Zombie Fighters is an open source, cross platform, 2d top-down, zombie shooting game.
UZF is a top-down 2d zombie shooting game. The aim is to survive as long as possible. Zombies will try to break in through windows and try to get you. Kill them and repair the windows to stay alive.
The game works on windows and linux(and possibly mac, confirmation needed).
You can chat to us on #uzf on freenode IRC.
Also you can use our forum