My first vote goes to FSN Assassin. I mean the one who swung large katana, not the one who threw away knives. I always thought that his background is somewhat tragic, being a character that people are still debating of his existence. He was fully aware of that background, yet still serve his contract until the end during the war. A real samurai spirit, IMO.
Second vote goes to Midoriba Itsuki from Shuffle!, a guy who is mostly annoying with his ever superior feeling towards the protag, but also a friend one can lean on in times of need.
Third vote goes to Uozumi from Kara no Shoujo. Well I don't have exact reason for this one. I just like him.