You want something completely useless and not practical.
Hindsight Lad
A monday morning qb that doesn't get payed telling persons what they could have done to win along with if they used specific different actions what the outcome would have been, but can't provide a plan to win before the fight.
The Bouncing Boy of DC Comics
As his name implies he has the power to bounce much like a bouncy ball along with making his body the huge shape like a soccer ball.
Wow that be useful if the Legion of Super Heroes ever required something to use like a dodgeball or a bowling ball. Otherwise not only is not exciting its mostly useless.
But does provide for a lot of clever funny puns.