My Patrick Ewing collection including 6 1/1 cards. Sold them to a fellow Ewing collector about 15 years ago when I stopped collecting, was over 700 individual cards I sold him
The main ones .... 2009-10 Playoff contenders Blake Griffin rookie (was a duplicate) for what it valued at the time - US$50. Also 2009-10 Panini Season Update Dual Rookie Autographs Blake Griffin/Stephen Curry .... that's in recent years. Going back further to my Sydney days .... 1997-98 SP Authentic Profiles Level 3 Chris Webber, 1997-98 STadium Club One of a Kind David Robinson, 1998-99 Fleer Classic 61 Chris Webber.
I don't really have any regrets, being that I haven't ever sold anything that high end. If I could get 1 item back tho it would be the 98-99 danny fortson autographics century marks that I had. While it's not a high valued card, they are quite hard to come by and since I did re-start the PC a while ago I would of liked to have it as one of the main cards in the PC.