What macros do you use? Which are your favourites?
Personally, I started out experimenting with macros when I was a very young Druid, with a /say macro that would tell targets of fly-by buffings who was responsible. I came to my senses quickly -- it was a remarkably spammy macro and I cringe when I see it still in my macro list. I've also used the macro functionality to change spell icons, as some of my different characters share the same icon for separate actions, a confusing situation. However, I've never found a 'killer' macro, though I'm happy to be converted.