[Saburo Sakai]

Ow

But there is such thing as tactical nuke.

They are typically very small yield (for a nuke) weapons.
The smallest nuclear weapon I know of that was detonated was code named Ranger Able and yielded "only" 1 kiloton. It was dropped by a B29 over New Mexico. I'm not sure of the year.

the smallest nuke i know of being detonated is fitted to cruise missiles, but then no one has detonated a briefcase nuke yet........