I've had a few where I got the wrong item off eBay...once I ordered a CIB
Deadly Towers and got a CIB
Legendary Wings instead, which basically put a new game into my collection instead of upgrading one I already had. The other time was fairly recent...I ordered
Wizardry VI for Super Famicom and got
Wizardry VI & VII Complete for Saturn. I wasn't too worried about it though, since it seems more people are looking for Saturn imports than SFC imports anyway, especially with lesser-known titles. Also helps me down the road, since I want to get every console Wizardry game at some point, so I'm not too worried about it