Let's see...
Charter Arms .357 Mag Pug. After 100 rounds of .357 through it, the guts started binding up. Sold it to a buddy, it seized on him, so I manned up and sent it in for repair. $100 later, it came back and was working. He dumped it at a gun show and bought a 7-shot S&W.
Ithaca M37 riot gun that some PD offloaded. It was in good shape, found out why. Sticky chamber would hang on every shell I put through it, even after massive polishing. Also, I didn't know how it worked when I bought it. The design is terrible. Sold it at a gun show for $200 and used the cash to buy truck tires. They stick because they're supposed to.
Sig P250 in .45ACP. DAO Trigger was terrible. I mean SW Sigma terrible. The size of the pistol compared to the ammo capacity was terrible. (No, I don't own a 1911.) Traded it off for a Kel-Tec P3AT, holster, ammo, and some tacbait for my shooting rig. Never looked back. Later, bought an FNP-45. MUCH better gun.
Walther P22. Wasn't a terrible gun, just wasn't what I wanted in a .22 pistol. Also, the 10-round magazine and mag disconnect made me mad. Got ahold of a Ceiner kit for my 92FS and I like that a lot more. 10-round capacity still aggrevates me though. But it's on a platform I need to practice on, so I deal.