Don't know if this counts but...
I wouldn't have ever thought of RenoxRude before Advent Children, but after seeing it they seem to be one of the more believable (not-really-canon) couples to me o_O. Especially after this (from this site):
(SPOILER)Reno: Hey, partner, this thing got any bite to it?
Rude: Shin-Ra technology at its finest.
Reno: Oh, so you made this?
Rude: If nothing else it's ... flashy.
Reno: Ooh, good.
Rude: You love it, I know.
Reno: Looks like today we're clocking out early.
Just something in the way the lines were delivered.