Urban Terror (1-1.5 GB)- Arena style combat merged with Counter-Strike and the early Call of Duty games.
Tremulous (300-400mb) - FPS/Tower defense hybrid pitting a team of bloodthirsty aliens against a detachment of marines.
Both have no microtransactions whatsoever, the 4.1 version of Urban Terror and Tremulous do not require an account.
Both free.
