This op-ed piece in the New York Times by a Penn law professor implies that if you shoot an intruder when you could have hit him with a frying pan instead, you might be in legal hot water:

The states impose carefully defined limitations on the use of deadly force in self-defense. (These rules are fairly uniform, state to state; most are based on the American Law Institute’s Model Penal Code of 1962.) A person may use only as much force as is “immediately necessary.” If a less lethal means of defense is available, the use of deadly force is illegal. Firearms are by law deadly force.

The implication is clearly that there is a universal, nationwide standard for the use of deadly force, and if you are not careful you will come down on the wrong side of it. This completely ignores the Castle Doctrine laws that have been enacted in many states.

Some states add a legal presumption about when a person is justified in using force against intruders. For example, Florida added a presumption that a person using force had a reasonable fear of death or serious injury to himself or another if (a) the person against whom he used force was illegally and forcefully entering a dwelling or occupied vehicle, was in the process of doing so, or removed or was attempting to remove a person against his will and (b) the person using force knew or had reason to believe this was occurring.

So much for waiting for immediate necessity. In Florida, you can shoot somebody in the process of breaking into your house or vehicle.

The author goes on to suggest that Tasers are a better choice, anyway:

A Taser works only within a limited distance, up to 35 feet for advanced models. But most firearm confrontations are at less than 10 feet. More important, the legal limitations on self-defense typically do not allow use of force at a distance. Defensive force is considered “immediately necessary” only when the defender can wait no longer, when the threat is “imminent.”

Yeah, I can see it now. Thug breaks into house, homeowner says, "Get out. I have a Taser." Thug pleads "Don't Tase me bro!!!" while backing out the door. Notice the author again makes the specious claim that you will be obliged to stand there waiting until the thug is right on top of you anyway, so why not Taser him first. Never mind that 14 states have passed laws allowing deadly force without retreat in the home (Castle Doctrine laws) and 12 more have laws allowing force without retreat when threatened anywhere (Stand-Your-Ground laws).