The list so far (in no particular order, and certainly not limited to just 10):
1. The Birotron (cool in concept; dismal in execution)
2. Any pre-M1 Chamberlin (Excedrin cycling headache # infinity)
3. Yamaha DX-7 (I hated trying to program it)
4. Korg M-1 (the very definition of "dross")
5. EMI 400 (as built)
6. Figgis Organichord
7. Vako Orchestron (from "disappointment" to "cute")
8. Vox Jaguar
9. Vox Continental (VERY mixed feelings about this one)
10. Mellotron Digital Symphony (the musical equivalent of "Gigli" and "Glitter")
11. Fender Rhodes
12. Chamberlin M-1 (based on feel, not sound)