Let's see :
~ Adol with his already big harem...yeah...since he is a knight it will be very difficult...
~ Archer and Rin Tohsaka
~ Daijuji Kurou and Sister Leica.[So...close...]
~ Sephiroth and Aerith[It was the original scenario,without Zack]
~ Auron and Quistis[I'm pretty sure she's...dead on for guys like him.]
~ Aqua and Zack[For Lulz]
~ Terra and Aqua[KH]
~ Rydia and Edge[Damn,why not?]
~ Rider and Archer[from Fate/Stay Night]
~ Akizuki Souma and his whole harem...yeah...as if.[Damn you Sega.]
~ Bayonetta and Dante?
Can't think of others...damn it's hard when most of your pairings are already reality.