I keep one pin at my parents' house - Star Trek Pro. Why? Not super shallow in rules (I don't get bored), great non-offensive theme for family, approachable for the kiddos, fun as hell, and it should hold most if not all of its value. Oh, and it has the best repeatable shot in pinball.
Unless you're not afraid of taking a slight hit of buying a NIB AFM and selling it later at a bit of a loss, I'd heavily recommend ST.