Nocturne is my favorite champ to play. I just love everything about him. All of his skins look great. Well, actually, the new look for the ravager skin isn't all that great. It looked cooler before though. The skins I usually put on are void and eternum. His spell shield is pretty funny. "hey, try to hit me with a spell while dueling. Thanks, more attack speed for me". His ult has to be my favorite ult in the game. I love Paranoia. Reducing the enemy's vision and rushing in on the carry is really fun.
Honorable Mentions: Ezreal, Pantheon, Aatrox, and Rammus