I like the baseball bat style; just wooden or aluminum, not necessarily with nails.
Improvised brutality; it says a lot about the character. A weapon that is distinctly modern while being so blatantly medieval. The character using it is often the same; they aren't out of place, this isn't a wannabe crusader, but it is someone who is purely capable of extreme violence, using what is familiar to them. They didn't train at a dojo to use this weapon. They don't have a sensei teaching them the traditional techniques. They are just prepared and capable, mentally and physically, to use violence as a means to accomplish their goals.