Megadeth have a pretty active eBay store where they sell all sorts of one-of-a-kind Mega-memorabilia like a pair of shoes Dave Mustaine wore one time and some $80 wristbands featuring Dave Mustaine's actual sweat..
But in all seriousness, there are some really cool things up for auction, like the just recently auctioned Jackson Y2KV 1st Approved Prototype 6442 which was designed and used by Dave Mustaine.
Mustaine is a Dean guy now, but in the 90s his name was synonymous with Jackson Guitars. He designed this guitar in 1998 and appeared on many magazine covers with it. Here's the description from the auction:
Up for auction is this ultra rare Prototype Jackson Y2KV (J6442) With special branded Jackson logo on the headstock. This natural unfinished Jackson Prototype was designed by Dave Mustaine and presented to him on 12/23/1998, featured on several magazine covers including Guitar Magazine in 1999.
This was the first guitar with the final 3+3 Y2KV head, but with dot inlays, rosewood fingerboard, alternate knobs and a blade switch. The body shape was not quite finalized either, but this was the 1st approved prototype, used by Dave Mustaine as reference for the final prototype.
Anyway, this is a super rare item and it's crazy to see that it went for a total of $11,300.00. The lucky bidder better cherish this piece of metal history. If you paid $11.3k for a guitar would you actually play it or would you frame it, never to be touched again?