Primal said:
That's one way to determine an NPC's level ("counting magic missiles"

, but I was also thinking of *rings*, because a wizard who has no magical rings on his fingers is < level 11.
Player 1: Hey, does the wizard have any rings on his fingers?
DM: He's got one on each hand.
Player 2: Holy crap! He's epic? I run!
Player 3: Me too. Damn you, DM! Damn you!
Player 1: Wait a minute guys! He's got 1st level fighters for minions, and we had no trouble killing his henchman. He can't possibly be epic.
DM: The wizard waves at you and gestures at his rings, smiling knowingly.
Player 1: Oh jeez. Fine. I run too.
*later*
Player 1: What was the big idea throwing that epic wizard at us?
DM: What epic wizard?
Player 2: You know, the guy with the rings.
DM: The guy with the 10 gp nonmagical rings? Yeah, when you started to freak out about his rings, he figured you guys were idiots and played along to scare you. It worked too, and next week you guys get to clean up the mess you made by failing to kill him. Also, when word gets around, you'll all be the laughing stock of the adventurer's guild. He will make sure word gets around. HAW HAW.