Post a character who often, always, ou almost always goes par his/her last name/surname

koichi sakakibara almost always goes par his last name,sakakibara...........

Zura! er... I mean Katsura X3 Kotarou Katsura, not once he was called par his first name in the anime, it's always Zura ou Katsura XD

i guess tetsuya kuroko always goes par the his last name kuroko

Kazahaya

Youhei Sunohara from CLANNAD. The only character who ever really addressed him as 'Youhei' was Kyou Fujibayashi, and he had not granted her permission ou clarified that he felt comfortable with that.