Well, I've had a few I didn't trust very well. One Tauus loosened up really quick, and I sold it pretty cheap, but it was always fairly reliable as far as going "bang" when I pulled the trigger. I sold it to a fella that knew it was loose, and he wanted to return it to Taurus for refurbishing.
I also had a Springfield Armory "micro-compact" .45 ACP for a short time. It broke twice before I'd shot the first 50 round box of target 230 gr factory loads though it, so I got rid of it as "unreliable". The factory fixed the both problems, and it worked great when I sold it, but I was done with it.
But the worst one I've personally owned was a CZ 75B in .40 S&W. That thing couldn't get through a single magazine of ammo, no matter the type or which magazine, without at least a couple of jams (stove-pipes, FTE, and so forth). I sold it to a fella who figured he could fix it.
By far, most firearms I've owned have been 100% reliable, and the ones I own now all are. Once in a while we all encounter a problem, so we deal with it the best we can. I never feel right selling such a firearm, so when I do I usually end up selling it for less than it's actually worth, and I let the buyer know why.
But I won't keep a firearm that isn't reliable.
Daryl