Bonarpant from FFXI. Obvious reasons.
Kidding of course. I think they would all come from XI though because the interaction in single player games almost forces the characters on you. With XI you kinda had to be willing to do the sometimes meaningless sidequests or skipable missions to get to know NPCs.
Ayame. Got a thing for dark haired grils from the east who can skillchain with themselves. Also because she gave me sexy pants.
Very close runner up would be Ajido-Marujido. Minister of magics, creataru of the cardians and we are both history buffs.
Second runner up would be Sea Horror. Probably the most entertaining NPC for me just based on how much time I spent on the ferry trying to skill up my fishing. I'm sure everyone remembers their first encounter with this guy.
You fork over your gil and almost burst with anticipation waiting on the ferry to carry you between Mhaura and Selbina.Finally the ferry disembarks and you're greeted by the soulful sounds of the ferry theme and a bunch of then unfamiliar sneak spam. You mash the ferry door open hoping to catch a glimpse of a whale or even a seagull when suddenly... hentaicles
I know it sounds disturbing, but when you're riding the ferry back and forth for hours a day crossing your fingers for a single 0.1 or even a miraculous 0.2 skillup, the sound of noobs spattering across the deck of the ferry was actually quite soothing. FWIW I always helped raise them when we reached our destination.
Edited, Sep 17th 2015 2:03am by FilthMcNasty