The Collaborative International Dictionary of English v.0.48:

Chooser \Choos"er\, n.
   One who chooses; one who has the power or right of choosing;
   an elector. --Burke.
   [1913 Webster] choosey

WordNet (r) 3.0 (2006):

chooser
    n 1: a person who chooses or selects out [syn: picker,
         chooser, selector]