Do you like varied map styles like the original Unreal Tournament including Medeval Maps? Good Opensource Music? Varied weapons some with moving parts (pistols)? A lightning gun?
Maybe try out chaosesque anthology. It's 4.7 gigabytes of that stuff.

http://www.moddb.com/games/chaosesqueanthology

It's all opensource, all of the time, and Divverent suggested the name.
And based off (is a fork or mod of) of xonotic and nexuiz.

Remeber raiders of the lost arc (but in antartica)

Prefabs so you can build a map quickly:

(Also: 48 weapons, want to add more, hit a code wall... well a mental wall because I can't figure out how to extend it, but it has been said to be easy)