Adcom GFP-565 preamp (early Nineties). Highly touted by the Mags but extremely ordinary performance. Replaced with a Classe 6. Now you're talking...
Another was the Magnepan MMG speakers (mid Seventies). Were pleasing to the ear until I heard some Conrad Johnson "Synthesis" floor standers which were clearly superior in every way. Granted, the CJs were 3-4 times the price but...
Lastly, for whatever reason, I've never been able to warm up to Audioquest cables. Not extensive exposure but never seemed to keep them more than a few months. I did own and enjoy their "Lapis" phono cables for a few years.