From Rap Dictionary
Baseball bat. "Hi, Claude again...You remember I told you about my cousin when I was 15 Well, the year after that, I killed this kid, Louie bashed his head in with my Louisville slugger hahaha I got away with it haha but erm I wanna apologize to Louie I'm sorry Louie hahaha" -- Eazy-E. ((intro for) Louisville Slugger)
Louisville Slugger was the brand of a very popular wooden baseball bat. It was made in Louisville, Kentucky; a "slugger" is someone who hits the ball very very far.