You know, the guy that decides how champions are changed in order to keep things as balanced as possible.
Who do you buff and who do you nerf? You're the head honcho, so you can buff and nerf anyone for any reason. Or no reason.
I would totally redo Trynd's ult. It would give large amounts of rage, armor, move speed, and AD for a few seconds, but he'd still be fully killable. Because seriously, **** invincibility on a dude like him.
I would boost the AP ratio of Teemo's shrooms. Because I LOVE AP Teemo, but he's just not viable enough.
I would give Singed a new ult. He moves fast enough already, his ult just makes him total overkill. It WOULD be a long-range gap closer, but I haven't decided on it's exact nature yet.
I would make Mundo's ult cause him to be totally immune to any movespeed debuffs or root-including debuffs. He needs to be able to go where he pleases.