A "Mitchell Arms" I think it was called, in .22 mag - a turnbolt. There was a REASON they were being blown out at $125 in the early 2000s.
A Brazilian Mauser in .30-'06 - if the bore is darker than the pits of carlsbad caverns, don't buy (an early lesson for me many years ago).
I'm sure a few others, but those stand out.
Oh, there was a Chinese single shot break action .177 pellet gun which was junk, also. On the whole, not that many which fit the criterion though ("regretted"). A lot more regret with handguns than rifles.