A keychain sized THWACK! When I attempted to print it after making it smaller, the ball end of the hammer wasn't sticking well to the build platform, so I imported THWACK into Blender and booleaned out a cube from the top and the bottom to create more of a flat spot. If you have had the same problem with a regular sized THWACK, just go ahead and embiggen this one.

1: Print. 2: Attach keys or whatever. 3: Hit things.