My fav niche that has recently died in the past 6 months would be reselling macbook pro chargers on amazon.com Its a funny story how I got into it. I was browsing ebay for things to resell and I came upon this ad that was $17 for Qty 2 of the macbook pro chargers. I noticed that this price was typically for 1 on ebay. So i purchased this auction thinking maybe it was a mistake. Well I got 2 in the mail. SO I decided to buy 50 and guess what. I got 100 in the mail. I then quickly decided to make a purchase of 100 so I get 200. That was when my luck ran out. After that they caught on that the ad was messed up and they accidentally put the price of one unit on a 2 unit auction. I was able to resell these on Amazon for about $25-$45. I had a nice system going on. After I sold them all I did some digging online and found a manufacturer in China. I was able to get them to send me 100-200 at a time. I didnt want to sit on a lot of them. I was able to sell that many in 2-4 weeks. Ill tell you what though. Those amazon guys are rough. Its a mob of sellers that will gang up on you and buy your stuff just to give you negative feedback. All mostly Asian too. Always underbidding you too. Now (check it out for yourself) The prices are $10-$20 on amazon along with 10 times the amount of sellers their was when I was selling these. Anyway. thats my story. Oh.. my second best dead niche would be credit card terminals. I would buy lots of them on ebay for about $50 each and resell them for $150. Mostly hypercom t7p and some veriphones. Now you cant even pay someone to take those off your hands.