By 'work' I mean actually submit the other guy. One that comes to mind is Jones vs Vitor. Yes, it dislocated Jon's arm, but Jon survived, and whooped Vitor's ass after that. I also remember Kevin Lee escaping a locked-in armbar in his last fight, shortly before he was submitted with a triangle. Any other examples? Some guys' arms are just unbreakable....it's not MMA, but check out Vinny Magalhaes being completely unfazed by a fully-locked armbar from Werdum of all people. He also went on to win the match.