The Suncom Slik Stik - My favorite multisystem joystick.

I have two of these, and I've found that they're fantastic, especially for maze type games like Pacman. The reason for this lies in the short stick and round ball at the top, making it easy for one to use it more like an analog stick on a modern controller with the thumb over the top of the stick. The button takes a little getting used to, but the rounded shape enhances the joypad-grip friendliness.