Dissidia seems to have gotten some people making some odd couplings. Cloud and Terra seem to be the most popular.

Personally, if one of the FF guys was going to be with the others, it would be Squall and Tidus. Both their relationships are pretty fake to begin with, so no worries about them crying for their girls. Lord knows, "Mr. Sunshine" makes for a good counter for "Soldier Boy". The best part will be how Squall treats him like trash and every time Tidus tries to object for how he's being treated, Squall will give him a bored look and tell him "Whatever" and then proceed to do erotic things to Tidus' tanned ass. It would be awesome, like an FF version of Gravitation.