If we're talking stoppages, as opposed to catastrophic failures...
... then the stoppages I've encountered were caused by operator error, once - at the time, my P220 had Hogue rubber grips that extended a bit below the lip of the magazine well, and I had failed to fully insert the magazine - it was flush with the Hogues, but not with the mag well. (Changed out those grips for some smooth Hogue cocobolos, and the potential for that problem went away.)
Others were caused by a combination of magazine springs (my Kahr PM9; replaced the springs and the problem went away) and a magazine the gun just didn't like (the 7rd mag for the Kahr - I've heard that any little finger pressure on the mag extension could cause hiccups - I traded that mag for a 6 rounder with a guy who knew my 7 wasn't working for me - he felt it was worth the risk, since his PM9 liked 7rd mags).
Not sure why my SIG C3 kept having FTRB issues, but after checking on TFL and the 1911 forum, I saw that C3's of that year and earlier were having a lot of those; I eventually traded the C3 for another P series SIG.
I never had a stoppage with my old 92FS Centurion. Never had one with my P239. Never have had one with an M9 on a qualification course. Never have had one yet with my DW CBOB (although that's still new). Never had one with my CZ PCR. Only had some with my CZ75B when I intentionally tried to induce them, by not cleaning the gun, to see how long it would take. Problems only started when the feed ramp went past "fouled" to pretty much "sludged."
A friend of mine has had several that were ammo related, as he was learning to handload. His initial runs of .45ACP were too weak to cycle his pistol. The third batch and subsequent have been fine.