That said, I have a terrible habit of smacking CTRL+ALT+BACKSPACE while attempting to hit CTRL+BACKSPACE. Yeah, I know. One kills the previous word and one kills the X server...
I've never really bothered to plug that up. This morning, I did it again. I did some digging:
Option "DontZap" "yes"
There. Now I can hit the wrong combination all day long and I won't bounce my X session. What a helpful little config option.