A unique variant of the GRA baseball bat named "Louis' Slugger" can be found in Doc Micheals' house near the starting bed leaning against the counter with it's mods, the bat can be repaired like any other of it's kin and uses the normal GRA mods.
It's attack is higher than a normal bat as is it's health, it has the bighorner knock back effect on hit.
I mostly made this as a personal mod to be played with the Zombie Mod made by Kalizar http://www.nexusmods.com/newvegas/mods/37393/? and I feel it's lore friendly enough.
The effect has a name which can be seen in the effects tab of the pipboy called "Home Run Loui".
You will need the GRA DLC for this work obviously, also all you need to do is place the file in your data folder for the game as it's a simple name/stat tweak mod without unique meshes/textures ect.