masochist

from WordNet (r) 3.0 (2006)

masochist
    n 1: someone who obtains pleasure from receiving punishment
         [ant: {sadist}]

from Moby Thesaurus II by Grady Ward, 1.0

20 Moby Thesaurus words for "masochist":
      bugger, coprophiliac, erotomaniac, exhibitionist, fetishist,
      narcissist, necrophiliac, nymphomaniac, paraphiliac, pederast,
      pedophiliac, rapist, sadist, satyr, scotophiliac, sodomist,
      sodomite, transvestite, voyeur, zoophiliac