Syp wrote a blogpost about five small features that he would like to see in all MMOs. The first one of these was the ability to loot with only one button.
So far the best looting I've ever seen was in Tabula Rasa, where you simply had to run over to corpse to loot it. Obviously, given the action oriented gameplay, this was a very important feature. Then, later, I used the AOE looting in Rift - which is again a lovely feature. And here is the third best one, from Vanguard.
What does it do? First, it will stop harvesting - there is a limit based on your skill for how much you can harvest from a node, and when you reach that limit, you will want to stop harvesting, loot the node and move on. Obviously, if you are not harvesting, it will try to loot whatever your current target is, and switch to the next corpse in range. With a few keypresses you will loot everything around you that you can.
To create this macro, all you need to do is click on an empty quickslot, and type in the text to the Macro window. I usually use the = slot, because it is easy to reach, but I don't usually use that one for combat.