Skarrrnneerrr!!!!
I bought him a couple months ago, and he was by far my best purchase. I went ad/tank Skarner jungle when I First started playing him, I wrecked.
Then I tried straight AD jungle, I wrecked.
Straight tank jungle? Haven't lost a single ranked with it yet.
Then I decided to try full AP Skarner top... That went really well (surprisingly) and AP Skarner works really well on aram. It has great duel (With nashors tooth) and very effective burst and sustain with his AP scaling shield.
He's probably the most versatile champion I've ever owned, and by far my favorite. He has wonderful utility. A Speed boost that ramps up slowly, Scaling shield, Low cooldowns, A slow, and an AMAZING lockdown (His ult).
If you ever load up a match and are stuck against a fiora/yi/zed/akali/kat/Pretty much any assassin ever that has no extremely strong disengage (And even then, it's still super tough), you will win almost every single time. Seriously, at least try him out.

Or you can try Malzahar if you like mid, and Irelia If you like top.