I know someone who AD Akali jungles, or used to.
While not that far fetched, Support Ashe works well and builds into a frightening off-carry.
Umm, Mana-warwick is scary. You just have to rush Manamune fast, so it's not too reliable. Actually, Spell Pen Warwick mid is sorta funny if you're laning against someone like Kassadin or Fizz.
Oh, Tank Brand. A friend of mine plays this. And has not lost a game that doesn't have something awful mess it up. Literally, Brand built as a tank, dishing out CC and HP% damage. It's frighteningly effective and a pretty good lane bully mid.
Nami also works pretty well as an ADC. You do really need to know Nami, but of all the supports, she has a good base range, I believe the highest base attack speed and damage of a ranged support. A steroid to her auto attacks. (her E) and Nami generally has to auto attack pretty often due to her long CDs. I've also seen her built as an AP bruiser, sort of like Kennen.
The old fashioned AD Annie is sorta classic odd playstyle for the champion.
Umm, as soon as her rework is out, Sejuani's going to be a pretty scary support with a level 1 Alistar Combo. People've talked allot about jungle Leona, and having tested it recently, it really isn't that bad. The triple-reset's what does it, and her damage can really get brutal with typical AD jungle sortsa builds.
Oh, AP Trundle. Becoming a tank by nuking a tank with a rather scary DoT ultimate. Dunno if it'll still be possible in the rework. But it's still sorta lulzy and funny.
Oh, and AP based Xin Xao. Relying on the ult's percentile to health and unlimited sustain from his W (even on towers) as well as reasonable ratio for his E.Though, admittedly this isn't much of a dramatic change for Xin in playstyle, but you'll be generally less tanky, but more pushy. Generally I'd still throw a Sunfire cape on though. You're melee, and burst'll shut ya down'n all.