Up until recently I would have said my BK2K. I would just dump it back in the garage after each pinball show, leave it in there until the next show (or maybe set it up for a while indoors) and everything would work fine on it each time. It has been a real workhorse over the last five years or so.
I had left it in the garage over last winter for eight months or so, and I set it up indoors last week - and it is now sulking with many GI lampholders not working, including a lot that are soldered onto circuit board strips, no 75 volts to the pops, display problems and I have had to replace/adjust several microswitches on the playfield. Looking like many more hours work to get it back working properly again!