WordNet (r) 3.0 (2006):

wise guy
    n 1: an upstart who makes conceited, sardonic, insolent comments
         [syn: wise guy, smart aleck, wiseacre, wisenheimer,
         weisenheimer]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "wise guy":
   Gothamite, boldface, brazenface, chutzpanik, hussy, malapert, minx,
   pup, puppy, saucebox, smart aleck, smart ass, smart-ass, smarty,
   smarty-pants, swaggerer, upstart, whippersnapper, wise fool,
   wise-ass, wiseacre, wisehead, wiseling, wisenheimer, witling