So, for me, it was a 20 gauge pump action shotgun I inherited from my father. He received it as a gift for being part of a wedding party. It was a 1 of 5 gun, wood furniture selected by hand from the assembly line, and said furniture was send out for custom wood engraving. I was in a tight spot for money with a child on the way, and he wasn't in much better shape, so he told me to sell it and call it a day. I would sell my 93 Ford F-250 IDI project, my gaming PC, every single thing I owned including my cell phone if it meant I could get it back. The worst part, too, is I can't even remember the make or model.
What I couldn't get rid of fast enough was as Savage Arms Model 93 in .22 magnum. The bolt, no matter what I did, rusted constantly. I finally gave up when after a green scotchbrite and WD-40 scrubbing session to get rid of all the rust, I cleaned it and baked it in the oven for 2 hours on warm to get rid of any residual moisture, practically dipped in Hoppe's, and set it in storage for 2 weeks. When I pulled it out, not only was the bolt speckled in fresh rust, the bolt handle was too. I sold it for $80 IIRC.