Has to be Oblivion: it's the only title I've ever played where I deliberately tried not to push the thing to hard, lest it went pop. Just look at the bug lists on the unnofficial wiki, and you'll see it goes on forever. One quest is completely glitched, with the reward getting stuck in your inventory and eventually causing the notorious 'permanent stat increase' error, where an item's effects become irreversible. How do things like that get past testing?
Fallout 3 is much better put together in general, although that too trips up here and there.
Fallout 3 is much better put together in general, although that too trips up here and there.