A bit of a niche within a niche maybe, but if you ever wanted a portable PDP-11, now's your chance.
http://www.cosam.org/computers/pandora/simh-3.8.pnd
Simulates the following machines:
Data General Nova, Eclipse
Digital Equipment Corporation PDP-1, PDP-4, PDP-7, PDP-8, PDP-9, PDP-10...