Kerry Wong has written an article detailing a simple hardware hack to make your mouse capable of doing rapid firing:
In this blog post, I will show you a simple hardware hack to make your mouse capable of rapid firing (or automatic continuous clicking). Of course you can always resort to software mods to achieve the same goal, but admittedly doing so in hardware is nevertheless more fun and as a bonus you also get an extra button. A video demonstrating this hack can be found towards the end.
For a typical mouse, whenever a button is clicked the output voltage level from the button changes between high (e.g. Vcc) and low (e.g. Ground) and this voltage level is in turn translated into the clicks. So the idea behind this hack is simple, if we could connect a circuit in parallel to the mouse button and automatically change the output voltage level we would essentially achieve the same effect as physically clicking the button.
More details at Kerry Wong’s blog.
Check out the video after the break.