When I pick Riven or Renekton I become a lot more balsy than usually. Normally I play defensive, only going in for the kill when I'm 100% sure (outside of unforeseen circumstances like a gank mid fight) that I am going to kill the enemy, but Riven and Rene make me want to do stupid shit that get me either tons of flaming or tons of praise, depending on how it works out. I get ganked? I try to win 2v1 instead of trying to btfo to the safety of my turret as fast as possible. Oh, one enemy chased me too far and now he's alone? Who gives a crap if he's fed Vayne on full HP and I'm 10% with lost lane, I'm going to try and burst him in the next bush!
So, what champ do you do stupid shit with that you normally wouldn't?