I've sold several that I wish I didn't have to:
Joe Jackson RC, 1915 Cracker Jack Jackson, M110 Cobb, E125 Wagner, E121 & '33 Goudey Ruths....N172 Phenom Smith.....E90 Speaker.....T3 Cobb and Johnson....'53, '54 and '56 Topps sets.....M101-5 Felsh SGC70.......whew....hold on....let me wipe the tears..
How about this?
Whats the one card you had a chance to buy.....you didn't buy it....I mean a rare card.....or one that you would never be able to obtain now.....one that exploded in value over the next few years?
Mine you ask???
T210-8 Jackson......kick myself in the A$$ everytime I get in and out of the shower......probably a low end "2"....for under $8000...

..hang on again....wiping more tears...and kicking myself (and I'm not even getting in the shower)