The one component that you wish you had not bought

A brand new $4,000 turntable ( I won't mention the company's name because they make good turntables). It's just that I had forgotten all the problems with vinyl, pops, clicks surface noise, having to clean the records, set up etc. Give me a good quality DAC anytime. Although the kids (those under 30) seem to be fascinated with the turntable and are always asking me to play some records GEEeeeeez.

A pair of speakers that were not a good fit efficiency wise with my amplifiers.  Sounded great but hard to drive them to their best

The KR 842 tube based amplifier. Stuck with it to this day. No support from KR when the transformer blew,so I'm got stuck with a worthless amp. I keep in the attic as a reminder to never buy anything from them again! Average sound at best and garbage build quality.

Musical Fidelity NuVista M3 integrated.  All bling, no substance.
Simaudio W6 monoblocks.  Build quality was poor and the sound was hard to explain, but I didn't like it.

pdreher,

I almost bought a Nu-Vista 3D CD from a recycler this week. Couldn't believe it was at a recycler, (but I digress). Listened to it briefly and thought it sounded OK, maybe even better than OK. Anyway, during my second demo it started to skip slightly. I was done with it at that point. Strangely, I did buy an immaculate Pioneer Elite PD-65 there which I'm using with a Benchmark DAC 1. Great combo!