Originally Posted by
Duilliath
AP Champs I recall off of the top of my head - not necessarily in mid lane:
Orianna, Ahri, Fiddlesticks (jungle/support), Lissandra, Fizz, Ryze, Twisted Fate, Elise, Karthus, Kassadin, Karma, Annie (Alex Ich played her), Rumble, Malphite (Froggen played him mid iirc), Kennen, Zyra (support), Diana, Eve (jungle / top), Gragas (top, mid, jungle).
I don't watch the OGN, but from what I understand, a champion like LeBlanc is still played there.
Mind you, this is not necessarily a complete list. But it already is a list of 20 champions.