Rikku would do a good pairing with a somber, depressive guy, i.e. she would make him lighten up and he would make her be less goofy. Gippal is just the same as her, and so is Tidus. Bo-ring!
Some say Auron would be a good pair (way too old IMHO), but in my fanfic I paired her with the rude, dark bloke from Gunners Gauntlet. Nooj was just too ugly and had Leblanc and which other dark and broody male is there ?