I like Kennen. You can harass pretty well with auto attack at 5 and W combo, or hit them with your Q if they forget to hide behind minions. Once you hit 6, if you've harassed them enough, or even if they over extending, you can almost always get a kill and then snowball from there.
My second favorite has to be Twisted fate. I can't say enough how awesome it is to have an on demand stun, and an Ult that teleports you across the map. I have scored so many ganks by queuing up a gold card and teleporting into a fight. Not to mention your sustain is beast with your Blue card.