League of Legends (LoL) Question: Good champion to spam on smurf?

Since I'm most likely going to level another smurf to level 30 over the course of the next couple of months, I was wondering: what's a good champion to spam on my smurf?

Now, don't get me wrong: I'm not talking about champions that snowball hard or anything like that, I could care less about stomping noobs in order to boost my ego (because yes, getting good scores vs bad players would obviously make me amazing). What I mean is that I could use the games to play a champion that is hard to learn, but great once mastered. A way of "easing into it", I suppose. Any suggestions on a (mechanically) challenging, yet rewarding champion (doesn't matter whether it's slightly unconventional or not)?

Vayne, maybe? Fizz? Yasuo? Other suggestions?

Thanks :)