I haven't really had bad experiences with a gun. (knock on wood)
The worst gun I have ever shot was an LC9. That was the absolute worst trigger I have encountered. The guy who owned it was so proud of it. He couldn't hit anything with it either.
The worst I have owned was a S&W third generation .40. I have owned over a dozen third gen Smiths and they have all been great, except that one. I would have been a lot more accurate throwing the gun at seven yards then firing it. I let a couple friends try it. I always assume it's me. They concurred that it sucked and couldn't hit anything with it either.