trying to figure out how to use App Switcher on Lion I recently bought a used Mighty Mouse, the slightly older kind with a little button on top that scrolls. (could anyone tell me what to call this button?) 

I set the button to use the App Switcher, which I had never used before. 

App Switcher opens okay, no problem there. and I can go left and right between them. but I can't actually open or switch to the app or, for that matter, close them. I can use App Switcher using the keyboard, though, thanks to tutorials. but I can't figure out how to do it with the mouse. 

so how I can actually use App Switcher using the mouse? FYI, I use 10.8.4.
Use the Mouse System Preference. There is a setting for each button on the mouse - including the nipple like one on the top. On my iMac I have this set to Off, but there is an option for Application Switcher, which if you chose that it would allow you to switch application by clicking the nipple button. I just tried this and it works, though I might not leave things set this way. If you don't like the idea of a nipple button, it's also called a mini mouse button. Oh, I'm using Mountain Lion too