Previous cabinets have used every imaginable kind.
Current cabinets.
Cocktail. Has a microswitch behind the left coin return button on the coin door.
Big wooden cabinet. Has enter, tab and escape buttons on the panel. This panel was pre-drilled by a previous mamer, if I had done it myself then they wouldn't be there. This cabinet also has 2 pinball buttons on each side (also pre-drilled, I wouldn't have done those myself either), which I seem to fairly often remap as service switches, pause buttons, throttle and such.
Giagantor cocktail. I'll probably do the coin return switch trick again.