I must admit, I don't really know much about the ZX81. It was a bit before my time. I personally grew up on the later 48K/128K/+3 Spectrums.
So why do I have one in my collection? Well, I picked this computer up purely by accident at auction. I was bidding on, what I thought was, a Sinclair Spectrum 48K bundle (with some games, books and magazines). After I won the lot and opened it up for a closer look I found this little ZX81 buried deep inside. An unexpected bonus. It worked too, although I didn't expect a monochrome display!
It came with a few extras; add-on keyboard, 16K RAM module, joysticks, and a few games. The strangest/most interesting one being "X-Men" by Amba Software.
- 21st March 2016 - Purchased for £20 at auction, along with a ZX Spectrum (boxed!) with games, software and magazines. Bargain!!!
- 11th Oct 2020 - Purchased a second ZX81 at auction (along with a boxed ZX), mainly for the 'outer sleeve' for a ZX81 box. A bit sad... but for a mere £48 I couldn't resist.
Games & Software
- 1K Games - Artic Computing Ltd : 
- Cassette 50 - Cascade Games : 
- Football Manager - Addictive Games : 
- QS Defenda - Quicksilva : 
- Reversi (also known as Othello) - Moi : 
- Spectrum Special 2 - Shiva Publishing : 
- Star Soccer - Watson Software Services Ltd : 
- VU-CALC - Psion Software Ltd : 
- X-Men - Amba Software (Can't find anywhere?!?)
I hope to restore/refurbish the ZX81 at some point. It's looking a little tired.