In my opinion any character can be deemed "op" if they are in a lane with a noob and get fed early game. I've yelled OP at more champs than I can count when we have a noob on our team who feeds.
I don't really feel that any champs are OP unless fed and used well, the only one I feel is OP is End Game Poppy, it doesn't matter if she's fed but if she's built properly and the game lasts long enough she can 1v5 the entire team if they don't have an entirely CC team
Tryn - Never dies
Twitch- as soon as you attack him me disapears :/
Shaco- I hate his little turret things, and its always disapointing when
you finally kill him, and you realize its his clone -.-