My favourite will always be the C.H.I.P. by Next Thing Co[1].

I still have one. They were priced towards 9 dollars, had on-board bluetooth and wifi when the Pi didn't and was significantly smaller. Sadly the company couldn't make it work. They also had a "Pocket C.H.I.P." which was a small display and keyboard you could plug your C.H.I.P. in.

Some company did buy their work and is planning to sell the boards and some variants as as the Popcorn Computer, but it has lost quite a lot of its charm.[2]

[1]: https://en.wikipedia.org/wiki/CHIP_(computer) [2]: https://popcorncomputer.com/