WordNet (r) 3.0 (2006):

practical joker
    n 1: someone who plays practical jokes on others [syn:
         prankster, cut-up, trickster, tricker, hoaxer,
         practical joker]

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "practical joker":
   Artful Dodger, Casanova, Don Juan, Machiavel, Machiavelli,
   Machiavellian, actor, bad boy, bamboozler, befuddler, beguiler,
   booger, buffoon, bugger, charmer, counterfeiter, cutup, deceiver,
   deluder, devil, dissembler, dissimulator, dodger, double-dealer,
   duper, elf, enchanter, enfant terrible, entrancer, faker, fooler,
   forger, funmaker, gay deceiver, hoaxer, hood, hoodlum, hooligan,
   hypnotizer, imp, jilt, jilter, joker, jokester, kidder, knave,
   leg-puller, little devil, little monkey, little rascal, mesmerizer,
   minx, mischief, mischief-maker, misleader, pixie, plagiarist,
   plagiarizer, playactor, prankster, puck, ragger, rapscallion,
   rascal, rogue, role-player, rowdy, ruffian, scamp, scapegrace,
   seducer, spoofer, tease, teaser, wag