Useful list of stuff.

[iamchickenlover]

http://en.wikipedia.org/wiki/List_of_free_first-person_shooters

I found this useful if you are stuck with crappy pc or are really cheap like me.
and all of these are not blocked on my school proxy!!

 

[JogaBonito1502]

Out of those I've played BZFlag, Soldier Front, and Tremulous. Trem is the best IMO.