WordNet (r) 3.0 (2006):

sledgehammer
    n 1: a heavy long-handled hammer used to drive stakes or wedges
         [syn: maul, sledge, sledgehammer]
    v 1: beat with a sledgehammer [syn: sledgehammer, sledge]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "sledgehammer":
   bang, baste, batter, beat, buffet, bulldozer, coercive, drub,
   flail, flap, forcible, hammer, knock, lambaste, larrup, maul,
   paste, patter, pelt, pommel, pound, pulverize, pummel, rap, spank,
   steamroller, strong-arm, thrash, thresh, thump, violent, wallop,
   whip