In Excel, you can hold down the shift key while you click a toolbar button to get different functionality. The one I use most often is the Increase Decimal button. Shift-click that button to decrease the number of decimal places.
One that I didn’t know, until I read a post by Beth Melton, Office MVP, is that shift-clicking the underline button creates a double underline (font underline, not cell border). I probably haven’t used a double underline ten times in my life, but next time I need it, I will complete that operation faster than I ever have.
Which shift-click buttons do you use? Maybe there’s some more I haven’t discovered.