AP Varus and Glacial Augment
AP Varus benefits the most out of Glacial Augment from my experience and I can't imagine other champions that could synergize as well as he does. The build is:
1
2
3
4
(You don't get both Banshees and Zhonyas)
5
Boots 
First off because of Hurricane you can perma slow like 3 people with Glaical Augment which is busted. Then you got the active on GLP which is 5s 50% AoE slow which is insane and helps get your ultimate corrupting onto everything. That's basically it. Inspiration: Glaical Augment, Minion Dematerializers, Intelligence, Biscuit Delivery / stop watch Sorcery: Mana-flow Band, Scorch
Early game you get Hextech Revolver into Nashors. After Nashors + GLP you ideally go hurricane unless you need zhonyas which I've find is always amazing to have and just provides so much more safety.
Excited to play more AP Varus tomorrow. I go bot lane btw because why not, it's safer and I can make plays easier. You still want to start doran's blade or cull and max abilities in this order Q->E->W->R.
The combo is usually 3autos -> Q -> 2 autos -> W _> 2 autos (W consistent consumes blight stacks)-> 3 autos Q When ulting cast E right away and it'll consume the blight stacks for you. You can ult + hextech GLP to make it reallly easy to corrupt everyone.
AP Varus NEEDS a mana item in order to spam his Q and E which are necessary for his blight stacks, Hextech GLP is the best item for that and super synergizes with Glacial Augment. AP Varus is best Glacial Augment user.