Mr. + Ms. Pac-man
Each year I visited a friends house we played it for HOURS each time. And I mean like 5+ hours.
I saw one within driving distance of me and bought it. I spent a lot of time on making it pretty.
It's a great game and no one even understands how to play it competitively. I don't think it's the best Bally ever but it has a unique set of rules, all the original pac man sounds, and a legit video mode from 1982.
One reason I don't see it getting a lot of love is because whenever I see one at a show, it NEVER works properly and is trashed.
I do not see myself ever selling it and have even considered hacking the rom to add some rules to the game.