Never really got a problem with any parts as such, I find that part of electronics fun.
I HATE wiring though...
I've built a
modular synthesizer, and I can tell you the absolute worst part of that is hand wiring all the sockets and switches & LEDs from the panels to the PCB.
I've got the solid wire earth loop down to a fine art, but hate, HATE,
HATE stranded wires.
Ok, another pet hate is lead-free solder... The RoHS crew can go shove their tin-whiskers in their landfill (but that's another rant altogether)...