Most classics that I encounter on location are always in beat down condition. It simply comes with the territory. If it is on location today, then chances are pretty high that it has been on location continually since back in the day.
Galagas and Ms Pac machines seem to be in the worst shape of the bunch. Followed closely by Centipedes.
Although I did recently encounter a Tempest on location that was in fairly decent condition, and working all the way. That Tempest was the first vector I had seen on location since the skating rink traded in their Asteroids for a Pit Fighter back whenever Pit Fighter came out.
Other older games I have seen on location recently include Sunset Riders (4-player boardset in two player cabinet), Bad Dudes (dedicated), Centipede (beat up, and not on), tons of Ms. Pacs, Donkey Kong Junior, Space Invaders, Joust, Crossbow, Galaxian, Rush 'n Attack, and Pole Position II.