First, I'd make sure the nukes would be weak enough to only destroy a small city. No reason to nuke a state, most of the people in the nuclear crossfire might not even deserve it.
North Korea is a good example for a target, but those who suggested it aren't considering what that means. It's not the people's fault they're being brainwashed by their own militant government. They're starving because thanks to their oh-so-great-dam they can't farm rice to feed their own people. If it wasn't for the resources they bribe out of other countries by threatening them, they'd be starving a lot more. I'd nuke the military staff in Pyongyang and down Checkpoint Charlie, opening the borders between South and North Korea. But maybe Kim Yong Ill's son will do just the right thing and get into peace talks with South Korea on his own. Here's hoping.
Then there's Iraq/Iran/Syria (Sorry), but that again puts innocents at risk, and I'd do nothing different than what is happening in those places already, except crank it to eleven. Yes, most of them go nuts now over the koran-burnings that took place (even though no other country so far complained about all the burning flags so far, flag-vendors must love this), but again, brainwashed into false security, this time via religion. So a mini nuke for each of their governments. Better check your seat twice in parliament next time.
Also on the list, yes, America. However, since there's no government left what-so-ever, certain CEO's of corporations and the real behind-the-scenes jerks get some grade A Gamma bursts (Wait, do they prepare for that? Is that why they all usually have the fried-chicken-brown tan?
).
There's also Russia, but that could trigger WW3. While Americans would hold back from firing straight away (even though the nukes are falling apart, hence two new reactors, yay -.-) because the F22's are grounded, the nautical fleet close to the drydock for repairs and the troops just came home from a war. No one in the military will enter another one for some time now. But Russia's Government wouldn't care that much about the aftermath as it would about prestige in their political ranks. So, again, it's down to Putin. As in under the seat.
In the long run, a nuke isn't even cost effective for the task at hand. It would only take a couple well placed shots from a drone/siper rifle. The only ones hit are usually never the real men behind the curtains.
Then again, I don't even need a nuke or assassins. At this point in our capital system, all you'd have to do is Hyperinflate a couple of resources on the stock market, drive people to withdraw their money from banks, and then start robbing houses when no one is home. Then burn the cash.
All of it.
Oh wait, you meant it jokingly who I'd nuke?
Umm, no one.