Resetting or updating a widget!
This is such a great tip, I just found out about it myself and I was so excited when I first used it. Many widgets keep old information and they don't always update the way they should. I have experienced this a lot with the ESPN widget included with Mac OS X: old hockey match didn't go away and new one were not up to date. Another example is you enter information into the Yellow Page widget and you wish you could just erase it with a simple click. The best is it works with all widgets! You just have to click on the desired widget, hit command-R and Boom!