Red Eclipse

Open source first person shooter with all the latest bells and whistles. The agile gameplay is fun, allowing you to use walls to run on and kick off from or perform double jumps or jump off high perches. Cooperatively build maps online with other players. As it is built from the Cube engine (but entirely redone from the ground up), it allows for smooth game play on lower end machines and lower bandwidth. Lots and lots of gore. Team members and opposing forces are easily identified (if a little bland). Many features like cross-hair radar and impulse jumping have been copied and revamped from other games, hopefully augmenting familiar gameplay. I for one found the cross-hair radar a bit difficult to get used to at first, but it does help to stay focused on targeting and movement rather than camping -- which is where the game truly shines. One other feature that I have to mention is the auditory feedback for landed shots. As an opponent's health decreases, each successive shot landed gives a "pinging" sound increasing in pitch. Very handy, and unique to Red Eclipse as far as I've seen.