I've found open sights to be the MOST susceptible to damage or misalignment. Look at used rifles at gun shows and note how many have front sights bent or with beads missing. The military knows what they are doing with those front sight guards.
Open rear sights of the type with an elevation adjustment screw get out of adjustment with handling, even in a case, but fronts are most vulnerable simply because of their location. Old rifles generally had very very low beads, making them less likely to be knocked, but also very hard to see under some conditions.
Those plastic "fire sights" or whatever they are called are the worst! I was shooting with a friend who had one of those on the front of his T/C. He leaned the rifle against the bench while we walked out to check targets and when he picked it up the little plastic rod was on the floor in two pieces. I asked "do you really plan to hunt with a sight that can't even stand shooting on a covered range?"
A well mounted peep rear and a low steel blade front set into its' dovetail with JB Weld is about as rugged as you can get. :grin: