I've never been in a gun-for-self-defense situation, so, no, I've not had a failure in that context.
But I've seen pretty much any kind of common service/SD-type weapon have a failure (some ammo-induced, some from the gun itself). There are some extremely reliable guns in the world. There are no failure-proof guns. Keep in mind, over extended trials, the metric is "mean rounds between failures." Not "failures, yes or no." Shoot a gun long enough, and something will go wrong.
But since the likelihood of you really, really needing a gun to go bang is relatively low, if you pick a very reliable gun with a very low failure rate, then the combination of those probabilities gets you below the likelihood of just falling over dead from a heart attack or stroke. Learn to clear malfunctions quickly, and then quit worrying about it.