I'll take a crack at it.
Best friend: Link. We'd have a secret code of "Hyut-ha!"s where we could communicate and no one would understand a single phrase we're saying.
Spouse: o_O Well assuming that I'd have Poison Resistance EX (Fate franchise reference), it'd be Hassan of the Serenity for sure. She's loving, cute, and deadly. What more could you want in a partner?
Ally: I'm assuming this would be some character that I would team up with or something to fight my enemies. In that case, I'd pick Ike from Fire Emblem so I can be his Soren. Classic brain-brawn combo.
Rival: No question, Gary Oak. I'd look at his top 10% Rattata and ask him if he's too poor to afford an exterminator for his rat problem.
Enemy: Now this is a tough one. If I pick someone truly evil or villainous, I'd probably be dead within a week. I'd probably pick Dr. Wily to be honest; he's really not a threat, especially with my buddy Ike around, so it'd be fun to beat up his robots for practise or something.