When I get back home I'm going to make a point of asking my brother in law to give me some sort of run down on guns and maybe go shooting. I figure I might like to shoot somebody one day and I'd like to know what I'm doing when I do it. I would hate for people to say, "well he shot him but he didn't really know what he was doing".
I recommend the glock .40 or, if you want more stopping power, the glock 10mm (ammo harder to find, tends to over-penetrate). They are simple to operate (no manual safety, no hammer, SAO), rugged, and *extremely* reliable.
The .40 S&W round is standard issue for the FBI and a great number of police departments. It has excellent stopping ability against unarmored targets (Though I use talon rounds myself: I recommend Federal Hydroshocks to avoid someone calling the shot "malicious wounding").
I also recommend the compact or subcompact as opposed to the full-sized (Glock 21). IME: the long slide on the full-sized handguns tends to cause considerable "up" pull and lengthens the amount of time it takes me to get back on target. The smaller weapons, especially the .27, tend to push straight back into the palm of the hand, and so I can fire multiple shots more quickly without a penalty to accuracy.
The .45 GAP is superior to the .45 ACP because of it's smaller shell size, but it's also less common. I'm not a big fan of either, as there's too much drop at range (it's a low velocity round). The 9mm is OK, especially with a +P round and, again, hydroshock or blossoming rounds: but the .40 is simply better (esp in that it deflects less through light barriers, like a car door).
The only exception would be people with small hands. The grips on the glocks are substantial; which is why it's not usually the weapon I recommend for women (unless they have large hands).
