My favorite example of an "unfortunate safety habit" was a fellow who liked to allow his circular saw to swing down against his thigh at the end of every cut (don't ask, it sounds as insane to me as to you). This was all fine and well until the day he needed to make a cut with the guard locked up such that it didn't rotate to cover the blade at the end of the cut. It took a *lot* of sutures and stitches to put his quadriceps and miscellaneous blood vessels and connective tissues back together.
If people are stupid enough to ask me for safety advice it usually comes down to "think carefully about everything that you're doing". You can give people specific advice about riving guards and push sticks all day long, but if they're not attentive to what their bodies and tools are doing they're probably going to come up with some novel and gruesome way to mess up anyway.
Of course it's not just woodworking. I had a coworker (actually a fairly senior engineering architect) who literally amputated his own foot with a shotgun. I tried very hard to incorporate some variation of "we should be careful not to shoot our feet off here" into every subsequent engineering discussion in which he participated.