Mine would be neither tactical, nor exotic, nor strictly speaking for self defense.
It would be something that when I bleed out, my very small wife would feel confident she could maintain and operate despite malnutrition, fatigue, dehydration and probable illness, and pass on to several generations into the future without any tools, parts or special knowledge.
For me, the threat of a tsunami gave me laser beam focus on this question, as I had reasonable expectation that we would not be coming back to the stockpile at home, and that in the ensuing social collapse/martial law following, a highly visible weapon would be a liability (aka detrimental to survival). What I grabbed told me a lot about the way my mind thinks in a crisis.