Quickly responding to the verses alex.tan cites, point by point:
Genocide: situations in Israel's history where they were engaged in war against another. "Utterly destroy"ing your enemy was not done to be vicious, but to keep members of the non-Hebrew societies from living on and polluting the religious views of the Israelites. As has been explained in The Ten Commandments node, the sixth commandment when accurately translated isn't "Thou shalt not kill", but "Thou shalt not murder" -- murder, as distinct from judicial execution or waging war.
The rod of smiting: all of these listed are punishments for crimes against Israel, or situations where God is acting on behalf of Israel's (and therefore His) war effort.
No mercy: waging war again.
Sexism: Don't even go there. You're talking about the perception of relationships between men and women in a society two millenia and half a world removed from our own. Paul was speaking to a specific church in 1 Corinthians, about specific problems and issues, and generalizing them to humanity throughout history is something that should not be attempted out of context.
Slavery: waging war again (Continue to Joel 3:9).
Morality?: waging war again, mostly. Solomon's collection of wives and concubines was never credited to him as a good thing in the Old Testament --I've always felt that one of the proofs that the Bible is historically reliable is the fact that even the greatest religious figures (Solomon, David, Moses, Abraham, the apostles Peter and Paul, pretty much everyone except Jesus) are clearly shown to be screw-ups at certain points of their life. And as for the exerpt from Revelation, very few people dispute that that is a heavily symbolic book and that verses should be taken out of context with the greatest care.
Just plain despicable: You've got that right. Lot was a screw-up, too.
That's a whole lotta casualties: if you have issues with the use of numbers in the Old Testament, keep in mind that numbers are the easiest thing to mistranslate or miscopy over time. Reading through an NIV Old Testament will reaffirm this fact; that translation was created from as many existing source documents as possible, and most of the time when they disagreed, it was over a large number. Not to say that all numbers in the Old Testament are unreliable, just that that's something you should keep in mind if you find them unlikely.
Foreskin mania: Circumcision was Israel's way of having a man symbolically give his life and heart to God. Killing one's enemies and taking their foreskins would be symbolic of killing them in God's name.
Finally, a note: Plenty of people think that killing people for any reason should be verboten by a good God. Since this would preclude the waging of war against enemies or execution for the sake of justice, I don't. The God of the Old Testament took possession of Israel, the descendants of Abraham, as his chosen people, and protected them vigorously against other people and nations whose beliefs placed them at odds with Israel's own -- and make no mistake, there were religions which practiced things like child sacrifice that were very much at odds with Israel's beliefs.
You say you don't think these sorts of actions are ever acceptable during wartime, for any culture? There are plenty of pacifists today who think that war of any sort, even killing a soldier in self-defense, is unacceptable. Refer back to my last point.
In this multicultural society, this sort of approach is looked down upon and considered an "atrocity" without any further consideration. Whether that should be the case or not is an issue for another node.