source: http://nationalpost.com/news/world/north-korea-is-just-the-tip-of-the-stockpile-here-are-all-the-nuclear-warheads-in-the-world-visualized

I liked this visualization as it clearly indicates the size of nuclear weapons ownership by countries. It indicates that North Korea is only one country which own nuclear warheads. The visualization has used red to highlight the N. Korea and positioning of the visualization shows that N. Korea is the tip of the rocket.