I'm a bit torn between a splitting axe and a mace/morning star of some sort.
An axe offers better penetration and is useful for other tasks aswell but perhaps posseses greater risk of getting stuck. A mace is not as versatile but is highly effecive when making direct contact with the skull and is unlikely to get stuck. A mace is also easier to improvise and customize for individual preferences.
I'm going to vote for the Katana sword. Light weight, sharp, and should not fatigue as quickly compared to the heavy blunt weapons.
That one’s my vote for best. What are you putting above it?