In your opinion what is the SECOND best melee weapon for a zombie apocalypse?

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.