List of commercial games released as freeware

(from LifeHacker.com)

Hedgewars

Free worms-like turn based strategy game.

Need for Speed: Most Wanted - Tweek Guide

Tips to optimize the performances of this game.

Battle Tanks

"“Battle Tanks” is a funny battle on your desk, where you can choose one of three vehicles and eliminate your enemy using the whole arsenal of weapons."

For Win and Linux.

The multiplayer version is FOSS (Free, Open Source Software).

(from The Linux Game Tome)

Typhoon 2001

"... a freeware game inspired by both the Atari Jaguar hit game Tempest 2000 and the arcade hit Tempest."