Robin
http://i.imgur.com/ADFemyU.jpg
http://i.imgur.com/FnYkmmF.png
http://i.imgur.com/tejjZ3m.jpg
As featured in the Type-Moon character popularity poll:
http://i.imgur.com/VWURt2K.png
50: Cock Robin Mahou Tsukai no Yoru Votes: 1012
51: Saber Fate/Prototype Votes: 1008