The Collaborative International Dictionary of English v.0.48:

Quizzer \Quiz"zer\ (kw[i^]z"z[~e]r), n.
   One who quizzes; a quiz.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quizzer
    n 1: someone who administers a test to determine your
         qualifications [syn: examiner, tester, quizzer]