Urban Terror a free game, about a 700 MB download, used to require quake 3, but no longer. Runs great on os x, i get smooth 60+fps on my macbook pro.
Not really a single player game, but great to go fight some people online easily. Free for all, Capture the Flag or bomb mode are the best depending on what kind of action you're looking for.
Games are expensive. Want to play the latest headline-grabbing entry from EA or Activision? Be prepared to shell out $60or $100 for the real version with a name like “Ultimate Edition.”Maybe that’s why so many developers are extending their horizons into the free-to-play arena.
My favorite parts are the physics and how you can strafe jump (bunny hop in an arc) to get places quickly, knife and boots are fun to humiliate or if you run out of ammo, and if you can jump on someone's head from 10 feet up or more they get curb stomped. There are lots of maps to test these jumping skills, and running in arcs on ice makes you go really fast jumps: icyjumps: icy ones get pretty out of control by the end of the vid.