Worst pistol I've handled was a Steyr GB 9mm. While gas delayed blowback was neat, dirty ammo would not only jam it, it would LOCK it up solid on a fired case. Only solution was to let it cool off, then you could rack the slide. Seems like a serious design flaw in a pistiol designed for military use.
Worst ones I own:
Lugers are just finicky when it comes to ammo. Hotter 124gr ammo seems to = less jams. Last pistol I'd take out of the safe for home defense. More so because of HOW it jams, always seems like you need 3 hands to clear a Luger.
Custom Seecamp style DA ODI/Viking/Colt gave me fits for a long time, not reliable enough to use as a defensive arm, just a range toy, and an expensive range to have built at that. Still a neat piece that I tried like HELL to run as my IDPA pistol.
Only other issues I've had have been with bad ammo or a broken/improperly cleaned gun. Had a brick of WW Wildcat 22's that turned my Ruger Mk2 into a jamming misfiring zip-gun. Tossed the ammo, no more problems. Still leary about buying that brand. Also broke the extractor tip off my FEG BHP clone after 5,000 rounds or so, which made it FTE and led to double feeds and other nonsense. One I realized I had a broken part, no problem. Also pays to clean UNDER the ejector once in a while with a toothpick or dental tool. That spring isn't very big and over time powder/primer residue can affect the function of the part.
Guns, like cars require cleaning and maintenance, sometimes stuff breaks.