The Collaborative International Dictionary of English v.0.48:

Charmer \Charm"er\, n.
   1. One who charms, or has power to charm; one who uses the
      power of enchantment; a magician. --Deut. xviii. 11.
      [1913 Webster]

   2. One who delights and attracts the affections.
      [1913 Webster]

WordNet (r) 3.0 (2006):

charmer
    n 1: someone with an assured and ingratiating manner [syn:
         smoothie, smoothy, sweet talker, charmer]
    2: a person who charms others (usually by personal
       attractiveness) [syn: charmer, beguiler]