That would be Pakistan, of course, with an estimated 60-120 nukes of up to 35 KT throw weight, and India, with an estimated 45-100 warheads deliverable by ballistic missles, cruise missiles, and/or nuclear submarine-launched missiles.
Latest reports have Pakistan moving troops away from the Afghani border toward India, and the Indian Air Force probing for gaps in the Paki radar net.
In case anybody has missed this, here's the abstract of a 2007 study published in New Scientist regarding a limited nuclear exchange between the two countries:
A nuclear war between India and Pakistan could cause one billion people to starve to death around the world, and hundreds of millions more to die from disease and conflicts over food....
Earlier studies have suggested that such a conflict would throw five million tonnes of black soot into the atmosphere, triggering a reduction of 1.25°C in the average temperature at the earth's surface for several years. As a result, the annual growing season in the world's most important grain-producing areas would shrink by between 10 and 20 days.
Helfand points out that the world is ill-prepared to cope with such a disaster. "Global grain stocks stand at 49 days, lower than at any point in the past five decades," he says. "These stocks would not provide any significant reserve in the event of a sharp decline in production. We would see hoarding on a global scale."
Countries which import more than half of their grain, such as Malaysia, South Korea and Taiwan, would be particularly vulnerable, Helfand argues. So, too, would 150 million people in north Africa, which imports 45% of its food. Many of the 800 million around the world who are already officially malnourished would also suffer.
Weapons of Mass Destruction (nuclear, chemical, biological, or radiological) are not a chimera invented by Dubya and his boys, even though they never managed to find any in Iraq. The real threat of WMDs is also less that of a terrorist strike than of an unmanageable regional conflict in which one or both combatants employs them.
Cold, hard truth: if Al Qaeda detonated a nuke or dirty radiological device in, say, New York or Los Angeles tomorrow, we'd be talking a death toll of at least 10-12 million, but...
...and it is a fairly big but...
...we would not be talking about the same global impact as if India/Pakistan, Israel/Iran, China/Taiwan, North Korea/anybody start tossing them around.
What's amazing is that we have well-developed doctrines for fighting limited nuclear wars, even for deterring them, but the US does not have a set doctrine for limiting the damage of one started by third parties.
You have to wonder why this is.
The fact of the matter is this: modern military technology (developed primarily by the US, UK, France, Russia, China, and India) has made such wonderful advances that crude WMDs are within practical reach of most any nation with a decent tech infrastructure and even large sub-national groups like Al Qaeda or--something we really don't like to think of--a good thirty to forty international corporations.
Proliferation has occurred. Management and threat reduction is the new order of the day, and--surprise, surprise--unilateral US military intervention is unlikely to be the most effective tool for such over the next several decades.