Sorry, LoadedDrum, but I have to disagree. Rule #2, in my mind, is the absolutely paramount one: never point a gun at something you're not willing to destroy. It's the one that's absolute fail-safe if everything else goes wrong. The whole point of the rules is to provide redundancy, because people make mistakes - how many stories have we all heard about people who "knew" the gun was unloaded, then proceeded to put a round through a wall, a refrigerator, a car, a door, a floor, etc.?
When I dry fire practice, I aim the muzzle at a target on the wall. It's not something I want to destroy, but it's something I'm willing to destroy. The point is, rule #2 is the backstop for all the others. Even if things go horribly awry, and a round is chambered when you think it isn't, and somehow the hammer falls, even then nothing seriously bad happens.
As far as cleaning the gun, in my mind, if the gun is in pieces on the table in front of me, the four rules don't apply to it (though I habitually don't look down the barrel from the muzzle end, even so). As soon as it's been put together, though, the muzzle gets pointed away from me and anyone else who might be nearby.
You mention training scenarios, and I'm not qualified to comment, since I'm not a LEO, nor have I ever been in the military. But I admit I'd be surprised to find out that training scenarios are routinely conducted with real guns aimed at real people - does this actually happen? (Note, training guns that are only capable of firing paint or dye rounds are not "real" guns)
Anyway, I understand where you're coming from, that guns aren't magical, and if there's no round chambered or if the trigger isn't pulled, nothing can happen. But the rules aren't there because guns are magical, unpredictable things, they're there because humans are error-prone, unpredictable things. Think of it as risk mitigation. Sure, the percent chance that I'm wrong about there being a round in the chamber when I've just reassembled the gun is miniscule. But the consequence of being wrong could be ending someone's life. Never pointing the muzzle at anything I'm not willing to destroy is an easy way to mitigate that risk.
It's also valuable in terms of habit. If you habitually follow the rules, even when you negligently break one of them, odds are good that you're following the others, and nothing seriously bad happens.
This is the same way I always check my blind spot when I'm changing lanes, even when I know there's nobody there (I'm alone on the freeway, and have been for miles). It's good habit. And it potentially saved my life once: I was exiting the freeway, signalling to get off, and I checked my blind spot before entering the ramp. Good thing, too, since some [EXPLETIVE DELETED] was tearing along up the emergency lane, and would have rammed me. That one instance justifies all the blind spot checking I've done, and all the blind spot checking I ever will do. Just like all the years of carefully not pointing an empty, uncocked gun at things will pay off that one time it's not empty and it's not uncocked.
". . . eat Kosher salami!"
