Heavy stuff. How about a selective strike on all known nuclear targets for maximum effect, coupled with a decapitation strike on command, control, communication and inteligence. The upside:

1. No more nukes.
2. No more current regieme, which is clearly unacceptable by anybody's standards. (Holocaust denial, calling for destruction of Israel).
3. Ensuring that Iran (the state, not its people) is not a viable international threat for years to come.

The downside:

1. Exactly who is going to attack Iran? U.S. and U.K. lack political capital in their own countries. Israel? That option creates its own security concerns.
2. Guaranteed source of West hating homicide bombers for generations to come (not really sure that this would change anything in actuality).
3. U.S., U.K., and Israel isolated on the world political scene. I know that some do not consider this a downside, but the U.S., U.K. and Israel really should play nice with the rest of Europe, Russia and China.
4. Attacking Iran only emboldens other states. What is coming from the former Soviet central Asian republics, which are predominantly Muslim? And they still have Soviet nukes on their territory.

Parting thoughts:

A first strike by Israel, coupled with a military blockade of the country with support from the U.S. and U.K., is completely justified. How to sell it to the rest of the world, and the citizens of the U.S. and U.K., becomes the question.

A first strike by Israel using tactical nuclear weapons on nuclear targets is another possibility. I have a very difficult time justifying first use, but when one considers that the survival of the entire state is at risk and has been directly threatened by a sworn enemy, if first use is ever justifiable, it is now.

Damn, I just started WW III. I can still play poker from my shack in Montana, right?

Hey I know the President is in a tough situation, and am not bashing...

Really though, Iran is waaaaay out there when it comes to tolerance and pretty much every political speech I've seen from Iran's leaders, has a common theme, "Death to America, Death to the Infidels". Not that it is a new mantra to hear them chant, no need to get them more riled up than they already are unless it is for a reason. We don't don't taunt rattlesnakes for the heck of it. Letting them quietly hate and not giving reason to provoke them is better than lumping them into an "Axis of Evil" and then invading their neighbor.

Diplomacy with Iran will fail. Any group of people that considers the other side to be infidels that should be destroyed isn't going to stick to much of anything sign, if they sign much of anything to start.

The only diplomacy that can work is gathering support of other countries, until the UN agrees on a solution. Taking military action with out the support of the UN is simply wrong. I don't think the US or UK has the steam behind them to initiate this alone, but can be the steam behind another group of countries that do feel strongly about it. I'm sure there are other Middle Eastern countries that are opposed to the idea besides Isreal.