Quote from tomdavis:
I doubt that Iran would nuke Israel. Israel has at least 200 nukes of its own, about half of which are kept outside the country on submarines, surface ships and aircraft. A nuclear strike on Israel would invite massive retaliation. The Iranians are crazy, but they're not stupid.
Would Iran strike the US? Possibly, but unlikely. Any bomb made in Iran would have a uranium/plutonium signature that could be identified as Iran's. It's not like they could sneak a bomb into the US, set it off and then claim they had nothing to do with it. Again, they would be subject to massive retaliation.
A Middle-East feud that most people are unaware of is the one between Iran and Saudi Arabia. Saudi Arabia hates/fears Iran more than they hate Israel. Iran would love to be the boss of the Middle East and control all the Saudi oil. And I doubt that anyone would come to Saudi Arabia's aid if they were invaded by or nuked by Iran.
Bottom line: I doubt that Iran will nuke anyone; but if I had to pick one I'd say Saudi Arabia.