Do random NPCs like city guards respawn? I just killed a guard in Dragonsreach to fill my Black Star, and it occurred to me that if they respawn I could use them and the black star to power-level my enchanting skill. It wouldn't take as much money as buying a ton of soul gems, and I think I'm sneaky enough to kill every guard in the place without anyone noticing.

Yes, they respawn.

Almost any NPC/Mob with a generic name can respawn. The only exceptions are some quest related generic mobs/npcs.

Awesome, thanks!

Yeah, bandits, guards, travilers, soldiers, mercanaries, thieves, hunters and anyone else with a generic name will respawn eventualy, people with unique names stay dead.