Grado sr325is...
I had a pair of old 325s, and I thought they sounded pretty good, however, they eventually died a pretty slow death. I purchased a new set of sr325is, and didn't know how different they really were. I thought it was a break-in issue, but they are just waaaay too bright. They hurt my ears with how bright they are, and unlike the "Joe Grado" sounding originals, the new ones can't really be used for certain genres of music entirely. Admittedly, when used with a really well produced Post-Rock album, the experience is like no other... (Russian Circles - Station blows me away on the 325is, for example, but that's not enough to keep them, rather keeping them for a handful of records seems kind of silly to me)
I never use them, and I really wish I had the money to be used on something else. I think I will sell them or trade them for something that fits my tastes better, maybe a working set of "Joe Grado" sounding grados, or perhaps something entirely different.
We talk about buying, what about selling? I regret selling my Denon D1001s, since they no longer make them. They sounded just fantastic, probably one of the best closed headphones at their price and for a bit above. They had the largest headstage of any closed phone I have listened to yet. Sound projected way out of my head, it was indeed an eyebrow raiser.