I often get the 'crazy physics', where I open a door, and contents inside rocket around the room, like the door was booby trapped. This has its downsides. Once, I opened a door, and the contents inside flew everywhere, hitting one of the Jarls sitting in the previous room. I was promptly arrested by the guards because of it 
The only gamebreaking bug I have encountered was an invincible Alduin. Even resorting to a save just prior to the encounter didn't work. I had to restart the whole game, and try a previous saved game.
The only gamebreaking bug I have encountered was an invincible Alduin. Even resorting to a save just prior to the encounter didn't work. I had to restart the whole game, and try a previous saved game.