...and to an extent, the Sennheiser HD25
The first two were responsible for getting me into better quality headphones, so they at least had some purpose. The AKGs were supposed to be my portable pair but they leak too much and they don't sound all that great. They have since been replaced by the HD25, which I am grateful I got for cheap because I don't hear a $250-$300 (retail around here) headphone when I listen to them.
I bought my bro Klipsch X10s, he broke the jack within a month, worst purchase ever.
Fiio E11 and E6, frankly the E11 is a great amp, but somehow I always seem to receive defective products, even after RMA, I totally give up, jack failures/loss of one channel, sucks when you are overseas and your amp fails. As for E6, it wasn't resolving enough to me. I'm switching to getting cmoyBB or something like that for my portable needs. The E6 was 2 months old, 2nd E11 was 3 months old before it became faulty.
Fiio RC-UE1, I waited 2 months for my order for the RC-UE1, only to find out overseas(in Beijing) that there is a product recall. They failed 2 weeks after I gotten them. FML, currently waiting for a replacement RC-UE1. Hope I won't regret waiting 4 months for it, since my Fiio interconnects are all working well and fine.
Seriously FiiO I wanna use your stuff, they sound great for the price, but make it higher quality!!!
I made quite a few headphone purchases I regretted dearly. The top of the list includes:
1. Sony XB500 - Lots of muddy, boomy, sloppy bass.
2. Monster Beats Studio - Over priced and over hyped. The obvious reasons why I didn't keep this.
3. Sennheiser 558 - Overall, I did not like the sound signature of this headphone. Purchased it on sale for $120 and returned before end of refund period.
4. Pioneer HDJ 2000 - Nicely built and durable DJ headphone. Problem I had is it sounded like something I would pay $100 rather than a $300. I'm not a DJ so had very little use for a DJ headphone.
I can't say I've ever regretted buying a headphone. Some have not been for me. I always took it as being another step in my journey to finding the "right" headphone.
But all the Grados I've bought, I had to sell them or return them because they were too harsh for my ears. On that note, I regret buying the LCD-2. I actually really loved them, but I kept having build issues with them (the wood cracking). So I was really bummed about that. I might some day go back to them now that they have fixed the issue (using the new connector pieces and wood).
Currently rockin the HD-800 though, and am satisfied.