I have a couple I can think of off the top of my head...  Most of them deal with the same place, a local store in town that has come to really like me (as I am probably paying a majority of the costs keeping their business open).
First, an inverse story.  I walk into the store and take a look at their N64 games.  Inside, I see a Clayfighter 63 1/3 with a price tag of $55.  I pondered about this for a second when I realized that it must have been taken in as the rare Sculptor's Cut version that was only sold at Blockbuster.  I informed the manager on duty and he had it changed, though was a bit upset that whomever took it in lost a lot of money on the deal.  A week or so later, I'm at my parent's house and checking the used game carriers in the area when, lo and behold, I see a copy of the Sculptor's Cut for $5.  Whee, karma.
The next story happened a couple months ago.  I walked into the store and looked at their "waiting to be put in the right section" section, and I saw a copy of Suikoden with the double jewel case.  I already had the game, but it was only $20 and had the case, so I figured "why not?"  I got it while making my typical small talk with the workers, then went home.  After changing out of work clothes, I went to check the discs.  The Suikoden disc was in the first part where the demo disc usually is, but I didn't really pay that much mind.  They seldom take the care to put the discs in order.  So I open up the second part of the case, and there I find Suikoden 2.  I rushed back to the store and tell them their mistake, but they said that there was really nothing they could do, since they already sold it to me.  So now I have an extra caseless Suikoden 2, but I told them if the seller comes looking for it to let me know.
The Last Story takes place on Lazulis Island and is a great RPG, but my last story takes place yesterday.  I'm sitting at my desk at work, and my phone starts ringing.  I answer, and get 
"Hey this is <name> from <store>, there's a guy here wanting to sell a game that's going for really high prices online..." (I'd given them my number and a list of games I'm looking for before, I've built up quite a rapport with some of the workers)
-"Really, what's the title?"
"Pan...zer... Dragoon Saga it looks like..."
-"Are you serious"
"Yeah...  Looks like if he takes the offer we'll be selling it for $140...  I'll call you back if he decides to take it..."
A couple minutes later I get a text with a picture with the case and the price tag, and he says I can pick it up, but he has to leave at 5.  I take a look at the clock, it's 4:40 and I work about 40 minutes away.  I tell him I can probably swing 5:15, and he says he'll try.  I rush to my supervisor, and I must have looked like I was in a panic, because he immediately told me I could go.  I drove as quickly as possible (well over the speed limit 

) back to my town to the store, and marvel in the glory that was my new rare game.
So yeah, those are my stories today.