I'm hesitant to list some of the stuff I think has been guff, for fear of being lynched.
Aside from a couple of speaker models anything Rega I've heard has varied from ultra bland to just not very good. Biggest disappointment being a P9/Apheta combo, although to be fair I perhaps should have tried it with a fruitier cartridge before getting rid, but still, not my thing.
Heed Quasar phono stage. What a massive let down that was, it was a one off with a massive Heed PSU as well, just sounded of nothing really, I've heard better on board stages in integrated amps.
*The little external phono stages* most, if not all of the little one box external stages like the Schiit Mani, Lehmann, Slee, Rothwell type. I've probably heard a dozen and if I threw a rug over them whilst you swapped them around I wouldn't know that you'd changed anything, aside from the P75 in Dr T mode they're all a massive meh and not worth bothering with.
Not been too keen on the direct drive TTs I've tried either, although only a couple of Technics models - various SL1200s with various arms and an SL-150 with a Tecnoarm. Although thinking about it the Rega arms might be the weak link with these, I should perhaps try one with a decent arm first before writing them off.
Come at me.