In law enforcement circles, that sort of thing is called "less lethal" ammunition, not non-lethal, and I can tell you that from a self defense perspective, it's not something you want to use, ever. If, as a civilian, you shoot somebody with anything, you had better be able to justify the use of lethal force, and if lethal force is justified, why use anything less?
If you're just trying to scare deer out of the garden or something similar, that's a different story. Unfortunately, I've never used any sort of less lethal projectile other than trying wax plugs in primed (no powder) .38 shells that somebody on here suggested for shooting wasp nests down. The neighborhood raccoons no longer eat out of my garbage.