I second Mike's appreciation of Steve, and extend it to Mike's own contributions as well. I especially want to acknowledge Mike's point, in a subsequent post, that rights are merely agreements, and not god-given a priori entities. I think a lot of libertarian theorizing has gone off the track here. I would count as (vaguely) supportive of my view Starchild's questioning what rights would mean under anarcho-capitalism and Denny's point that we don't need laws against juggling vials of smallpox virus.
I like the approach of J. C. Lester's _Escape from Leviathan_: If you impose a cost on someone, you owe compensation. That's a principle I would expect to get pretty universal endorsement, even you intended to try to avoid paying such compensation. Then leave it to courts or arbitration agencies to work out the amount in particular cases. Over time, obviously, guidelines would evolve, though they would also be subject to change. I think that approach really obviates all the impossible questions flowing from the concept of rights or the nonaggression axiom. Some years ago _Liberty_ asked its readers what they would do if they fell off the balcony of a high-rise and miraculously caught themselves on the flagpole of the neighbor below--who then refused to allow them into his apartment. A surprising number said the only moral option was to drop to their deaths. I say, force your way in and then pay compensation for trespass. I would expect the amount of compensation due to be judged rather small. We can say, if we want, that I have violated the apartment owner's rights, but I'm not sure that adds anything to the discussion.
Quarantine is one of the knottiest real-life issues I've seen. But if someone with smallpox refused to quarantine himself, and recklessly or maliciously exposed others, I wouldn't be surprised to see him meet a premature death from other causes. Again, I would expect the compensation due his survivors to be determined to be rather small. No guarantees, of course, but there aren't ever.
As for owning nukes, don't we all know well enough by now the consequences of prohibitions on possession (among other things, that possession simply has to be concealed), and the wisdom of leaving the really effective weapons exclusively in the hands of government?