Professor X & Magneto
David R: They've have been portrayed as philosophical enemies since the very first issue of the X-Men. While they are at the opposite ends when there have been dire threats to mutants or Earth, they have pulled together to save the day for world saving glory (and the pounding required to get the job done).

For example we have Uncanny X-Men #200, where the trial of Magneto had the courts attacked by Fenris and Hydra. Magneto was kept together by Professor X and in turn Professor X helped Magneto hit every target on the board... and hit hard! In the Necrosha X, a rebuilt Professor X and a reformed rebuilt Magneto start to work together to build Nation X. When attacked by Selene and her minions the Professor turned the psychically restored pawns while Magneto handled the larger physical armies.

In clix terms what you have in Professor X & Magneto is a high cost figure that can penetrate anywhere on the map and make sure you feel it without having to actually get up into your enemies face. What's more, in mid or later stages they can not only hit you, they can strike then heal without having to take a break in their indomitable battles.

Cable & Deadpool
Dallas F: Cable and Deadpool because of their long history together, neither have been clixed for some time now and both are popular enough to make them a sought after piece.

Also Multiple men - being a kind of generic, you could field many of them and if put on a double base I think the sculpt could be made to look fantastic. Possibly showing one of them splitting. Considering the popularity of the previous Multiple men this would sell well.