Toribash
I couldn't see it as the best game I have ever played but I must say it is definitely one of the most fun singleplayer RPGs I have ever played, I'm loving it.

Fable: The lost chapters.

VIVA LA [pSy].
Toribash was really the first multiplayer/singleplayer game i played and ever since i've been hooked on it and can't seem to stop playing it and the forums are a very nice addition to the game giving various reasons for playing the game, so when you're not in-game you can be forum-active and vice versa.
You've Been GodSmacked