India v. Pakistan ...
Obviously people don't know their history here.
Most US think tanks and intelligence have believed since the mid-'80s that once India and Pakistan develop the bomb (which they both have now), they will use it against each other within the first 25 years. Today, this still seems to be the most likely and believable scenario by the overwhelming majority of intelligence of most of the world. People should really read up on the history of India and Pakistan and you'll quickly note the flash points where it will probably happen.
North Korea merely wants to use nukes for appeasement. So its very, very doubtful they will ever use them. China knows this and it defines much of their resistance at times to bring North Korea to the table, although the Russians have been far more cooperative because they don't like a nuclear power so close.
Iran is still up-in-the-air, although if they do get them, they will probably eventually use them. In the same counter-point, if the US knows for an absolute, undeniable and, more importantly, concrete evidence (at least to NATO allies, even if their citizens are against US action) that certain that certain Iranian facilities house them, the US will likely use burrowing (sub-surface, causing no airburst/mass destruction), tactical nukes to take them out.
People claim the US will because of WWII. If you're that ignorant, then you really should read up on the barbarism of the Japanese in WWII -- not to just the US, but the Chinese and countless other, smaller nations. The use of nuclear weapons by the US saved countless Japanese lives and unnecessary deaths of women and children as much as men and combatants. It was absolutely necessary to drop them on people, as even the Japanese military and, especially, the emperor would admit later.