This is my second blog here. If you have time, check my Katarina guide in my profile -> Blog.
So, I've been doing a really fun thing - testing out AD champions as AP. It was surprising that many of them were really successful. I test them in a custom game with bots, sometimes in PBE, sometimes in Live servers. So, here is the list I've tested so far:
OP damage with Cannon Barrage, OP heals with Remove Scurvy, OP nuke with Parrley + Lich Bane. One of the most viable ones after Lich Bane.
Even if she doesn't have any AP ratios, I've done a quadra only with Tumble + Lich Bane procs. Still has no actual damage, though.
AP Lee Sin:
A huge shield with Safeguard and quite big base damages, I've done quite well with Lich Bane procs.
Penta included, one of the best ones. After Transcendent Blades, 3 of her skills do huge damage, pushes the lane with a single
A quadra with a single Grand Skyfall! Was really fun, he was like a suicide champion, based around jumping on enemies.
I was amazed at how good he was. Hands down one of the best options. He does HUUUGEEEE damage.
IMO the best one out of this list, after farming Q a bit I destroyed an inhibitor with 2 Siphoning Strikes. Penta included.
The funniest one. It's so freaking amazing when you kill someone with 90 Caliber Net!
AP Dr. Mundo:
He could just stand near enemies and proc Lich Bane with Infected Cleavers and roflstomp anyone.
Did quite bad early game, but later on Dragon's Descent and Flame Breath were enough to do a penta.
One of the best options, does shitload of damage with Blighted Quiver.
Was actually worse than I expected, he could just proc the Lich Bane with Decisive Strike and spin around with no damage.
Was amazingly fun, dat Spirit of Dread too op.
On tie with Nasus as the most viable one. The damage she deals is unbeliefuckalievable.
Wasn't very good, bad AP ratios = pitiful damage and dying instantly.
AP Miss Fortune:
Also in tie as the most viable one, With Lich Bane all of her abilities do damage, I don't think I need to say anything else.
Decided to try it after the Siv HD guide. Was so much fun, much more than AD Rengar (a.k.a. my most hated champ).
Withhe did so much burst it's not even funny.
The worst one in this list IMO, can't really do anything, even bots manage to kill him before he can do anything.
Laughed so hard when he didn't die when I dived into a turret 1v5 and did a quadra. That Bloodlust...
Terrific AoE damage with enough attack speed, I think it would be very viable in normals. Maybe not as pure AP, but as Hybrid or tanky.
That was so hilarious, when he gets full HP with a single Hungering Strike, plus does tons of damage.
AP Xin Zhao:
Should also be viable in normals as Hybrid, adds more burst and sustain.
He was viable before his Q and R got nerfed, so it's obvious he's quite good.
Early game was really rough, but after myand he did huge amount of single target damage. And that heal is ridiculous.
These are all the ones I've tried so far. I didn't add champions like Tristana, Master Yi, Sion, because you know they're viable.
I'll add Twitch, Olaf, Graves, Renekton, Riven, Jarvan IV, Fiora, Rammus, Sivir, Darius, Yorick, Ashe. If you think if any more options, please tell it to me.