Israel has nothing to fear from Iran other than their arming Hamas and Hezbollah. Israel can take care of both nuisances without resorting to nuclear weapons. A nuclear attack by Iran would be a disaster for Israel, not fatal, but totally fatal for Iran. It would cease to exist and all its 73 million people would be dead. Ahmadinejad mouths off but he is not in a position to do something so stupid; a first strike nuclear attack by Iran is simply not going to happen. North Korea, if it has a nuclear bomb, would never use it first. That would end N. Korea. Neither Pakistan nor India would use a nuclear bomb. Russia and the US would never use a nuclear bomb on one another. The real danger is a dirty bomb or a nuclear bomb brought into Israel and exploded with the idea that the source would not be known. The US might be at some risk but not Israel since if it happened Iran would be assumed to be the source and they would disappear so they are not going to let that happen. I suspect the source of the bomb would not be difficult to determine in any case.
Death toll from car bombs in Iraq rises to 56 (AP)
from the article: Iran military head warns of 'heavy damage' should Israel attack