Dragon…wings…?
What evidence is there that it could work?
They didn't argue when stuck in the cell together on the Lunar Base.
Wufei said, "I've been looking forward to fighting you," in Endless Waltz.
Well, though there isn't anything specific in the show that I can cite as an example of why these two would work together, they are somewhat compatible. In other sections I've mentioned that Heero is going to need someone that he can think of as an equal for his partner. Wufei may or may not live up to that, but he is a dedicated soldier who also has no trouble living off his emotions. And there's no doubting that Wufei trusts and respects Heero—all the pilots do.
As the only two east-asian pilots, they certainly would make a handsome couple ^_-
What evidence is there that it wouldn't work?
Same argument for all of the other unlikely couple sections: not enough positive evidence. Both are distracted by other things/people. They don't spend any amount of time together and hardly even speak to each other until Endless Waltz. And during that time, it can hardly be argued that Wufei was acting sensibly. Wufei wanted to fight Heero because he was a worthy opponent—more than that, Heero represented the ideals that Wufei wanted to put to the test. In Wufei's mind where "might means right," fighting Heero was the only way to find out exactly what he needed to know about himself and his future—which of them was correct (for those of you that know Kenshin, think of Soujirou).
Thus, the only positive evidence supporting these two as a couple can be explained through the personalities of the characters themselves.
In conclusion
Heero and Wufei are both talented and strong pilots, and they respect each other. They may have differing views at some points, but all in all they're comrades—nothing more, nothing less.
