Spectrum

The Sinclair ZX Spectrum was one of the first widely sold home computers (way back in the 80s - I actually started out with a ZX81). It is also one of the most widely emulated (I won't even try to list all the emulators here, only the ones that stand out in one way or another).

I used to own a plain 48K:

...and later, a 128K "+3":

Old Favorites:

Highway Encounter

Resources

• 256-color versions of a few games

Emulators

• jsspeccy, an amazing JavaScript-based emulator.
• Perl-based emulator - this one actually made my jaw drop.