Dave Haynie is the only one I think.
Unfinished prototypes are tricky, if you include those then the rarest amiga will be one we don't know about.
The A2000 revision 5 is very rare, estimated as 5 boards produced.
"
While there are many Amiga 2000s in the world, the Rev 5 is extremely rare. As far as I know, only about five boards were made. The purpose of the Rev 5 board was simply to add higher density memory to the Amiga 2000. The original design used sixteen memories for a bank of memory, this design used four (there are two banks). This was the last Amiga 2000 motherboard I had all that much to do with.. At the time, the Rev 4.x was in production, and the new board was desired for new production, as the price crossover from the 256K x 1 to the 256K x 4 memories had been reached. However, the Rev 5 board was completed ahead of the need for it. So the PCB guys did some additional cleanup work on the design, and I think the FCC people got involved, too. Regardless, the resulting Rev 6 motherboards were plagued with problems (in fairness, some were due to the switchover to a 68000 with faster signals, that was also noisier). - Dave Haynie"
While A3000+ was estimated as 50 produced, however the majority were revision 2 boards (renamed AA3000). How many revision 0 & 1 boards were produced is unknown & how many of each remain is another thing altogether.
"Rev 0 (A3000+, Most components were socketed)
Rev 1 (A3000+, Completed audio sub-system, most components surface mounted)
Rev 2 (AA300)"
Revision 0, 1, 2, 4 & 7 of the A500 are unknown but they probably existed
