I actually don't use many macros. I have a hard time remembering what they do, let alone where the hell I put them on my action bars. Sadly, I'm more of a "point & click" kinda gal.
However, there is one macro I like to use every now and then. This macro I just love for when I'm in a dungeon, or raid, and someone keeps asking for "Recount" or "DPS meter". I press my handy-dandy macro and they see what you see in the picture below.
I borrowed/stole this idea from someone a few years ago. Can't remember if it was a fellow blogger or something I saw in some forums somewhere. But, I love it and have it in a handy spot on a few toons' action bars.