Getting MML2 was one of my favorite finds. I started getting serious about collecting back in 2008 or so, so I was on eBay trying to pick up cheap stuff all the time. I came across a misspelled auction for complete copies of all of the PS1 Mega Man games (8, X4, X5, X6, Japanese copy of DASH, Legends, Legends 2, and Misadventures of Tron Bonne) that was ending pretty soon. Luckily, I managed to snipe it at the last second and won for a total of around $26 shipped. Now, even though these games weren't as valuable as they are now (MML was going for about $7 for a complete black label copy, MML2 was around $45, and Tron Bonne was in the $90 range), I knew I had scored a really great deal.
Two weeks later and the package had never showed up. I contacted the seller and he was really spotty when it came to communication and he assured me that he was looking into it. I got really discouraged at that point--I figured that he realized that his stuff sold for WAY under what it was worth and that he was pulling the "oops, package got lost, let me just refund you" thing so he could relist the games and get a considerably larger amount of money for them. Luckily, I was just freaking out and the package showed up about a week later--turns out he had put down the wrong ZIP code.
Definitely not my best find when it comes to pure monetary value, but it's definitely one of my more memorable ones simply because of the situation and how much I loved the games.