I sneak into people's houses, take things off their tables and shelves, and put them into barrels (Otumeel's idea).
I also provide bandits and marauders with weapons that restore health to whoever/whatever gets hit with them.
I give rings with...interesting effects to guards: Resist Fire, Frost, & Shock 100% + Drain Fatigue 500 points/second. The put on the rings, then pass out from exhaustion.
I provide mages with prank amulets: Resist Magic 50%, Absorb Magic 50%, Fortify Magic 1000 points, & Silence , all on Self.
I cast a spell on Heironimus Lex that forces him to equip the Gray Cowl of Nocturnal.
So what fun pranks do you guys pull?