Yeah, Bump N Jump doesn't have a freeplay mode, but I hacked it a few months ago: http://forums.arcade-museum.com/showpost.php?p=1523579&postcount=44 . That's assuming you have the normal Bump N Jump (not DECO system, Burnin' Rubber, etc). Most of my hacks are quick fixes, and don't optimize for fewer ROMs, so sorry... there's at least 2 ROMs required (3 if you want self-test to not complain about bad ROMs).
DogP, thank you soooo much for making this hack! Yotsuya just burned these for me, & they work GREAT! You are my hero.
Getting all my games ready for Zapcon this weekend, and this was another Midway game that didn't like my Easy CoinUp or even a normal switch to add credits.
I'll gladly buy you a beer somewhere if ya wanna meet up. And/or if you want me to open the doors to Starfighters Arcade for a peek... I'll PM you my cell#.