I am still a noob at the game I admit, but Ryze was absolutely eating me alive with his snare when I was forced to mid for a few bot games last night. She's great at getting away if she isn't CC'd, but I couldn't actually take hits very well if I couldn't Valor/Stun/BW weave in and out of combat. Not to mention I could not use BW at all while snared.
Good news though, I like Riven enough to actually have a melee character I'm willing to work with! So I have my 5.
Janna (suits my playstyle waaaaay too well)
Karma (if she had Janna's range she'd be my favorite)
TF (I feel like I can't kill with him like I should but that low CD ranged stun is soooo addictive and helpful)
Heimerdinger (I actually bought this guy by accident and tried him for the hell of it, but wow. He is the best harrass character I have enjoyed using yet and suits my playstyle well. He might end up being my go-to pick for non-support characters)
and Riven (Jump in/jump out combo addict here).
There's a few others that are debatable for me that I'd like to play more, but I only have so much spare time for games in general, let alone a particular one. I'm sure I'll find more though, especially since I am still really new to the game.