Perhaps the most famous brand of baseball bat in the world. Beloved among office drones for that scene in Office Space when the three heroes take their infamously misfiring printer out into a field and bash it apart with saidbat.
To beat the holy hell out of someone or something with a Lousiville Slugger (or any kind of bat) is "to go Louisville" on them/it. Example:
"Christ, did you see them go Louisville on that printer?"