My favorite class is Comp 136
This applet is merely a simplistic demonstration of the pure raw graphics power of the Raster class. If you click a number, it cycles its colormap. if you click empty space, it creates the next number and starts it spiralling. The growth of the spirals is dependant on where you click; see if you can guess what its dependant on.
I recommend viewing it on a Fast PC or a Sun Ultra using the JDK appletviewer, as that will give you the best, most reliable performance. But hey, if you want to crash your browser, its your syscall.
Also I've noticed flaky behavior with the mouse click detect in the Java 1.02 event model. Try guessing where the sprite will be next before clicking it. (Yucky, I know. I'm interested to know if other people had this problem with clicking moving objects)