One of the Powder Gangers for the Booted quest decided his bound hands were no object, spawned with a cowboy repeater, ran around shooting at Legion and then got himself killed. Failed quest, reload.

Other than that...nothing too weird, the ordinary/common glitches and AI weirdness.
But this video where Vulpes spawned, climbed onto a cross in Nipton, gave his speech, then climbed back down is the funniest individual thing I've seen. Sure, they had to use the console to spawn him because he glitched and didn't spawn in Nipton, but it's still hysterical.
http://www.youtube.com/watch?v=WOfZDE5uqRE