In my first ever D&D game I played a half-orc rogue who was something of a jerk. The DM allowed me to have a ring of prestidigitation at 1st level for an -350 XP penalty. I kept the thing hidden from the other players as long as possible and co-ordinated some nifty stuff through the DM.
The most memorable prank involved a trip to a tavern. I burned a daily use of the ring to make everybody's beer taste like wine. It caused a lot of confusion among both the PC's and the players and jsut a teensy bit of suspicion about the tavern owner. Had it not been an online game, my cracking up would have given it away.