Creating a Medieval Lightsaber

First, you'll want to disable the lightsaber blade from showing.

SWEP.NoBlade = true
SWEP.SecNoBlade = true

Next you will want to change your lightsabers sounds. You can find out about that here

Lastly, you'll need to ensure your hilt model is rigged correctly to be used as a lightsaber otherwise you'll have some issues.
Heres an example model pack of medieval hilts you can use.
https://steamcommunity.com/sharedfiles/filedetails/?id=2805545169