If you have Logitech control center installed

[Ilgaz]

Many people won't care about installing it but if you have installed and if the software you work with doesn't need 3rd button:

Open logitech control center, doubleclick the 3rd button of mouse setting, select "open application" as job assigned, click "other" and select Pathfinder.

So, if you click third mouse (or wheel button) Pathfinder will launch. If its running, it will come to front.

I was using it as opening my home folder via finder but as finder got unpopular here for obvious reasons... :)

[bill]

I've got LCC, but I've got all 8 keys in use. I prefer to use Keyboard Maestro to switch to PF when I press cmd-[kybd]0. I've also got a key on my n52 set to switch to PF, but with 48 possible key combinations I keep forgetting which one it is.

[Ilgaz]

I forgot to tell its a trick for "logitech mouse only" users.

Of course, the keyboard etc possibilities are endless.