After killing Adam the clown by the rollercoaster in Wonderland Plaza, he will drop a chainsaw. Pick it up before you activate the control to stop the ride. After the intermission sequence, another chainsaw will spawn at the location. Pick it up. Get the Criminal book from the back of the bookstore where you find the Japanese tourists, and the Engineering and Entertainment books from the Book Store accros from the toy store and CD store in Paradise Plaza. These will give you three duration enhancers for the mini-chainsaws that you get from the clown, which will make these powerful weapons last for a long time. These chainsaws can kill Bosses in two or three hits and are great crowd killers.

After killing Adam and getting the mini-chainsaws he uses, grab the Criminal Biology, Engineering, and Entertainment books to make them last nearly forever. They are the best weapon in the game.