For me it,s my Assos bib shorts. I have had these 6 months now and i still think they are the most overated cycling product going.
That's a tad harsh. Like a lot of high end stuff, you are paying a lot for little differences. I agree Assos is over priced (for my purposes anyway) but I don't think it's overrated. IF I was someone that spent hours, day-after-day in the saddle (or a racer, where those minimal differences meant a lot) then I think I might be paying for, and appreciative of, the difference. Still, I respect your opinion!
For me, overrated is something bought on recommendation and with some expectation only for it to find its way to the back of the wardrobe, or the dusty corner of the tool shed. I've only a couple of things I can think of that fall into that category; firstly (and sadly for me, being an NZer) is a Ground Effects shirt - it really is quite ordinary and unexciting despite it's rave reviews - and, secondly, a extending tyre lever thing (can't even remember it's name!) that's no easier and more pfaff than an ordinary lever - I never reach for it.
Edit: just remembered something, a complete pile of crap and utter waste of cash; a handle bar extension thing, for putting lights etc on, Minoura swing grip I think...