Not the person you're asking, but on my macbook I frequently use:
two-finger swipe right (go back)
four-finger swipe up (overview)
four-finger swipe down (change between multiple windows of the same program)
four-finger swipe left-right (change virtual desktops)
pinch to zoom in/out
The first four would be easy to bind to a mouse button, but the pinch zooming is really handy.
I got sick of not having a pinch to zoom gesture on my Windows desktop, so I bound Ctrl to a mouse button and hold it while using the scroll wheel. It's pretty handy, I wish I could do it on all mice.
In a lot of Windows applications, and in the mainstream browsers, holding down the CTRL key and spinning the mousewheel gives you a zoom functionality. It's built in by default.
two-finger swipe right (go back) four-finger swipe up (overview) four-finger swipe down (change between multiple windows of the same program) four-finger swipe left-right (change virtual desktops) pinch to zoom in/out
The first four would be easy to bind to a mouse button, but the pinch zooming is really handy.