1. Xonotic is a fusion of Quake and Unreal Tournoment. It features secondary fire mode, loads of modes and original maps and foremost a really awesome community. I highly recommend to try out this title if you are interested in this genre. 1.0 is not released yet, but it's already very mature and fun, it's also completely free software. http://www.xonotic.org/
1. Warsow is a Quake with a unique twist regarding movement and graphics. It got that Borderland cartoonish look and it fits really well in this fast paced genre. It also features a "dash", that is that you can turn without loosing velocity and do walljumps etc. Loads of great original maps, and a active community. Highly recommended as well. Warsow has reached it 1.0 release and is has a free software engine, but the game assets are proprietary. http://www.warsow.net/