The Collaborative International Dictionary of English v.0.48:

Stickler \Stic"kler\ (st[i^]k"kl[~e]r), n. [See Stickle, v.
   t.]
   One who stickles. Specifically:
   [1913 Webster]
   (a) One who arbitrates a duel; a sidesman to a fencer; a
       second; an umpire. [Obs.]
       [1913 Webster]

             Basilius, the judge, appointed sticklers and
             trumpets whom the others should obey. --Sir P.
                                                  Sidney.
       [1913 Webster]

             Our former chiefs, like sticklers of the war,
             First sought to inflame the parties, then to poise.
                                                  --Dryden.
       [1913 Webster]
   (b) One who pertinaciously contends for some trifling things,
       as a point of etiquette; an unreasonable, obstinate
       contender; as, a stickler for ceremony.
       [1913 Webster]

             The Tory or High-church were the greatest sticklers
             against the exorbitant proceedings of King James
             II.                                  --Swift.
       [1913 Webster]

WordNet (r) 3.0 (2006):

stickler
    n 1: someone who insists on something; "a stickler for
         promptness"

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "stickler":
   Simon Legree, absolute monarch, absolute ruler, all-powerful ruler,
   arrogator, ass, autarch, autocrat, bigot, bitter-ender, bullethead,
   caesar, captious critic, commissar, czar, despot, dictator,
   diehard, disciplinarian, dogmatist, donkey, driver, duce, fanatic,
   hard master, hardnose, intransigeant, intransigent, last-ditcher,
   martinet, maverick, mule, nitpicker, oligarch, oppressor,
   perfectionist, perverse fool, pharaoh, pighead, positivist,
   precisian, precisianist, purist, slave driver, standpat,
   standpatter, tyrant, usurper, warlord