Olaf and Cho are probably the two best 2v1ers. Yorick and Gragas can work really well if they manage to get a blue buff (ie being in the appropriate lane and having a non-blue dependent mid). They'd work without it, but they're much stronger with. Irelia is also a pretty solid 2v1er.
Anyone with a solid clear skill and some tanky-ness or escape mechanism will work, like Malphite, Shen, Lee Sin, or Renekton. It doesn't necessarily matter who the AD and support are. They're either going to be a push combo or a kill setup, to take advantage of jungle ganks. The person fighting two will be under the turret the whole time, so who it is doesn't matter that much, except if its an Olaf, as he can farm reasonably well under those conditions and has a strong slow to help out when the jungle comes rolling in.