My sister has a pet pig (a 150+-lb https://en.wikipedia.org/wiki/Vietnamese_Pot-bellied); it lives in the house with everybody else and forages in the backyard. I can't say I'd ever thought of keeping a pig as a pet, but it's a perfectly fine creature, gentle when it's not being provoking, and intelligent and quite communicative.

I can't see it being "man's best friend" (dogs have a bunch of special abilities that pigs don't) but both pigs and goats play an important enough role to call them "man's best helpers"