Hesse H91 & Century CETME: Both H&K 91 copies. Both of them would pattern at about a 6" circle at 25 yards... While I would like a 91 platform, this next time it will be a PTR.
Bobcat BW5: MP5 clone that liked to jam at least once or twice a magazine. Although I think it was an extractor issue, I sold it off before I learned enough to diagnose and fix it.
Sig Mosquito: Could not finish a magazine without having some sort of jam issue. Sold it within a week of buying it.