Working in retail, I come across a lot of insane people that just love to tell their life story or some random tragedy that happened years ago for no reason. I'm working so obviously it isn't the best use of time to sit and listen to this crap. To get away from listening to their crap I usually notice a other customer "needing help" and go ask if they needed help. If they say no, I just continue on in that direction away from the crazy person. If they say yes, I help them and then move away from the crazy.

When NOT working, just ignore the person. They usually just want some kind of attention. Act like they aren't there and they will go away... or stab you. But at least the conversation will end!