Oblivion

I've been playing Oblivion for the XBOX 360, and I think it's pretty good. It has its host of little glitches, but it saves often enough that it's always possible to just go back.

My favorite personal glitch: fleeing from an enemy in the sewers, I jumped away, only to fall through the floor and into the water below. The walls of the sewer were solid from the outside, but were only visible from the inside. I could see into the rooms, but I was trapped outside. Fortunately, the game doesn't check whether there's a wall between you and a door, or I never would have escaped.

In the capitol city, there's an officious guardsman who wants to destroy the thieves' guild (of which I am a member). I saw him walking along the road, snuck over to him, and picked his pocket. Now I have the police chief's key to the city. Stuff like that is what makes the game worthwhile.