For me, it's Annie. Win or lose, I always enjoy being a pyro child blowing people up with my trusty teddy bear.

Lulu
BECAUSE DRAGON TRAINER

...Teemo

Taric because he's outrageous.

Hecarim, running at 700 movespeed to crash into someone before they see you is hilarious.

Zombie Brand

i love everything about it so much, but the death animation is probably my favorite part

problem is that the dying part isn't really good for winning the game

Lux. Looking at her makes me positive. even when i die. even when i miss laser. even more when i hit laser in a no-look shot(really amazing).

Playing as Lee Sin makes me laugh. Because everything can be solved by kicking.

Blitzcrank's really cute when he scratches his head and wobbles around

Jayce when I snipe people with my accelerated Qs