Glitches enrich Bethesda's work. The Elder Scrolls and Fallout would not reach the same heights without that anything-can-happen, chaotic feel that their excessive errors lend them—the feeling that at any moment the world itself can collapse or that everything will cease to be as you drop through the world.
Fallout 3 contains many eerie scenes of post-nuclear devastation, but the tensest moment in my experience with it came from a glitch. Here I am, wandering a desert, scavenging what I can, when the danger music plays. Spinning about, I find nothing. The music plays. A car-sized scorpion lunges at me, hissing, from inside a sand dune to my right.