Yesterday, our in-house IT manager was dumping a big cardboard box of obsolete cables and peripherals. In addition to me, this girl in the production department is a real scavenger, so we hauled the box over to her desk and started pawing through it like it was a treasure chest of booty. Among the tangle of cords, orphaned connectors, heavy power adapters, busted mice and ancient external drives, I found a Trackball Explorer, which Microsoft rolled out in 2001 for about $75, a king's ransom for such a device at the time. It’s since been discontinued.
I was excited to take it home to play Centipede via MAME on my PowerBook. It worked without having to install any driver software; all I had to do was plug it in and launch the game, and I was committing insecticide like it was 1984. Although Centipede is by far the most famous trackball game, Wikipedia has a list of ’em.