The G3 cube was a good idea but was overpriced, as it was inferior to the regular G4 in every aspect other than size. It was priced to be a 2000’s-era executive desk ornament, a relatively tiny market segment. A few years later a substantially similar product was released to massive success—the Mac mini.
The puck mouse was stupid, but it wasn’t as bad as people made it out to be. It was eminently useable once you got used to it.
Jobs’ biggest design failure has always been his refusal to acknowledge the importance of cable strain relief.
Also the third generation iPod. Yeesh.