Having thieves run up and try to rob you, but then stop and apologize once they realize you're in the Thieves Guild yourself.
The leather vats in giant camps that you can harvest mammoth cheese from.
The seriously psychedelic effect of drinking Sleeping Tree Sap.
When NPCs spot a dead body and gather around it, making comments like, "What happened here?", "What a waste," and, "Is he/she... dead?" If the group gets too large, a guard will even come by and say, "Alright, now, everyone back away. Let the law handle this. If anyone saw anything, step forward. Otherwise, step away from the body." If you don't vacate the premises and remain standing there with your weapon drawn, the guard might even take you to task for your suspicious behaviour. Seeing as he's got nothing on you, though, he lets you go on your way, telling you to talk to the captain of the guard if you 'recollect anything about the incident'. (The first time this happened to me I was blown away at how responsive the AI was to its surroundings.)
When hunters attack you for having let an animal free from one of their traps.
To name a few.
