My Gottlieb Jumping Jack pinball machine project has a lot of rusty old light sockets. Amazingly I got most of them to work by cleaning and soldering connections but the row on the light bar that match the drop targets were still flaky so I decided to try Yoppsicle Socket Free LED Sticks.
Yoppscles are LEDs mounted on a small circuit board. The newest version even includes resistors mounted on the board to remove flicker that often happens with LEDs on EM pinball machines.