Okay, I've found a few more freeware games that I particularly enjoyed, but I know these first two aren't for everyone.
5 Days a Stranger (
http://www.fullyramblomatic.com/5days/). This is a point & click adventure, and so it probably won't appeal to you. However, if it sounds interesting, I suggest playing it as it's a very short and enjoyable game. Also by the same author is
7 Days a Skeptic, which is the sequel to 5 Days, and so if you enjoyed that, this is one to play.
Deadly Rooms of Death (
http://www.drod.net/) The concept behind this one is pretty simple. You are sent by the king to exterminate some pests. Sounds easy? Oh, quite the opposite. This is a puzzle game, and a clever one at that. It starts easy, but the further you get into the dungeon, the harder it gets. (Wasn't expecting that, were you?
) You will go from killing roaches, up to Goblins and 'The Living Tar'. I found this one a good time-waster.
Wolfenstein: Enemy Territory (
www.slashdamage.com) This one is a multiplayer-only FPS, like AA, but quite a bit more fast paced. The gameplay is fast and fun, and has quite a few twists on the usual FPS formula. In each map there are objectives, unique to each team, that you must accomplish. Also, there is an XP system, and depending on how much XP you have, you will achieve different ranks and abilities. The graphics are good enough to rival commercial games, at least back when it was first released. The best part about all this is that it is free, and still better than most commercial FPS'. I really liked this one, which is saying alot since I can't stand most games of this type.
Oh, and did someone say Runescape?