This'll pretty much just be quotes since these have been refuted before.
"Imagine you are sailing your boat along at sea, minding your own business, when you hear a noise behind you. You turn around and find a bedraggled looking man climbing from out of the waves onto your craft.
"Thank God you happened by!" he says. "My ship sank, and I’ve been clinging to the mast for a day now. I had almost given up hope."
You nod solemnly at him, walk across the deck, pick him up, and throw him back in the ocean. "You see," you explain to an imagined audience of shocked onlookers, "he was trespassing. I came out here for some solitude, and the idea that now I’m compelled to accommodate him makes me into kind of a slave, doesn’t it?"
In most people's view and in most legal regimes, this justification is pathetic and you are guilty of murder. And I think that verdict is correct. (I realize some libertarians may disagree, and my argument may be unconvincing to them.) But what of your complaint that you are being enslaved by being forced to take this unwelcome passenger?
The fact that you cannot toss the man off your ship does not compel you to go anywhere you were not going before. If the interloper says he would really prefer to be let off in Boston rather than your destination of New York, you can tell him to bugger off. Most importantly, you are not compelled to keep the man aboard one moment longer than is necessary to get him to safety. At the first moment you reach a populated land, your responsibility for the man’s fate ends. Yes, you are inconvenienced, but that is all – and in a decent society, when you are in a unique position for being able to save someone’s life at the cost of a minor inconvenience to yourself, you are obliged to do so." - Gene Callahan
"The point of abortion is to kill the child, and most abortions dismember and/or poison the child. But some abortion choicers frame abortion as merely termination of the pregnancy; if a child dies because she can't survive being evicted into the hostile environment outside, that's tough, they say. Still, eviction is clearly gross negligence, and if it results in harm, all who participated in the eviction caused the harm and violated the non-aggression principle."
"Writing in Power and Market, economist-philosopher Murray Rothbard points out the sufficiency of "Every man may act as he freely chooses" as a definition of liberty. The proviso usually added -- "provided he respects the like freedom of others" -- is rendered redundant by the universal quantifier "every." For, as Rothbard notes, if one man's freely chosen action is the assault or robbery of another, then the victim is deprived of living or acting as he chooses and liberty does not obtain.1 This is just the situation with abortion: The control being sought is not over one's own body but over another's. That is not freedom, there being no coherent notion of freedom for all which includes the freedom to coerce."
- Both quotes are from Libertarians for Life; look here for more on this argument.
"You are kidnapped and dragged aboard an airplane right before a transatlantic flight. A while into the trip, the owner of the airplane insists that you are trespassing, and orders you to leave. Of course, you are thousands of feet above the middle of the Atlantic, but this does not matter. Neither does it matter if the owner was the one to kidnap you, as the owner retains the right to withdraw consent at any time. All that matters is that you, at the current moment, are on the owner’s property without consent. Now, the owner opens a door, and pushes you out. Through a meat grinder. Keep in mind that this is entirely justified, as the owner has the right to remove you from the plane. Not letting the owner do this would be forcing her to let you out when the plane reaches its destination.
Of course, this is absurd." - Me (also adresses the claim that those who are anti-abortion want to force women to give birth)
Actually, Libertarians for Life has addressed pretty much all of the even semi-intelligent pro-abortion arguments. Comment on this post if you have one they have not adressed. If you have a problem with one of their rebuttals, tell them; they're always interested in constructive criticism.