shihonage
Second Variety Games
katana being much better than an European broadsword in all respects
Katana is hard enough, but also flexible - it reverberates so it doesn't get stuck when going through human body. It's long enough but not exceedingly so. It has weight, but is not heavy enough to lose effectiveness if you lose muscle mass. It allows powerful cutting without losing balance or creating large openings for counterattack.
If I was stuck in a zombie apocalypse and had to choose a blunt weapon, I'd find an abandoned dojo to loot, and stock up on katanas.