Source : Webster's Revised Unabridged Dictionary (1913)

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

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

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

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

Source : WordNet®

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