No-click Mouse?

TheRealZappa writes "For quite a while now I have been looking for a mouse that would not make any "clicking" sound when the buttons are pressed... Does it even exist? So to all you quiet-pc amateurs and hardware hackers... Can it be hacked? Can it be bought somewhere?" Sure it exists, I think they call it a "trackball" or "touchpad". Seriously, I've never had a non-broken mouse that didn't click.