UltiMax, also known as MAX Machine, VIC-10 or Vickie, was supposedly planned to be released by Commodore in 1982. It was made at the same time with a computer called VIC-30 - that, of course, is these days better known with the name Commodore 64.
The system was based on cartridges. It didn't have ROM of its own; there was a BASIC interpreter for it, on a separate module. Clearly intended as a "game console" rather than a serious computer.
It is actually interesting to note that Commodore 64 has specific "UltiMax mode" for cartridges and is fully compatible with UltiMax. This cartridge mode is mostly useless, but it has one known common application - many turbo cartridges (such as Action Replay Mk VI, I'm guessing here?) use UltiMax mode for taking control of the machine when you hit the "Freeze" button.
Apparently, UltiMax machine had a very stripped-down C64 in it - only 4 kilobytes of memory, only one CIA chip, no ROM; The keyboard was one of those hideous rubbery things. (*cough* Philips Videopac *cough* MSX *cough*)
The machine was apparently released, eventually, only in Japan with name "Max Machine". It flopped - due to the price. The only reason why it remains interesting is due to the curious compatibility mode in C64 and even C128...
Commodore did not learn their lesson from UltiMax, however. Much later, they made a "console" version of Commodore 64 called Commodore 64GS, and it was likewise a flop even when it was technically more interesting. (And let's not even mention the Amiga-based consoles...)