The usb controllers made for the recent mini systems (NES, SNES, Genesis, etc) make great accessories for the mister. Add a couple of usb arcade sticks and you can really play almost any classic retro games as it was meant to be played.
And then there are all the classic computer cores even including the PDP-1!
The Amiga core is fun, AGA, 2 MB chip, 384 MB fast. It supports hard disk images, so you can do a hard disk based Workbench installation and load games and demos practically instantly (and safely exit to Workbench) using WHDLoad.
Arcade cores are fun as well. Just like in childhood, but less hungry for quarters. :) Recently played with arcade Gauntlet core a bit for example.