The only guns I own that have never failed are the ones I've never shot, and those with fewer than 100 rounds through them (that goes for borrowed guns, and observations of others' guns, too). There are just too many variables within the system - gun, ammo, shooter, environment - for there to be perfect function over any sort of extended period. I've found a LOT of people give mulligans when answering this question, referring to "ammo failures", "mag failures", "limpwristing", "test firing", etc., and so absolving the gun. If the gun doesn't go bang, there was a failure.