This is what I tell my students, from beginner through multi-engine instructor: it is not a propellor - it is an xx HP Cuisenart (xx depending on the engine, of course). Do not reach through the prop arc, regardless of how the engine was shut down, unless you have a really good reason (and even then, try to think of another way to do it). Never curl your fingers over the prop. Always be in a position to get away from it if something happens.
I can go on, but you get the idea. My "other" career is in an industry that has equipment that can kill you without even missing a beat. I've learned from what we teach about safety is that the second you become complacent in anyway, you're a statistic that hasn't been written down yet.