Just a quick slash command to remove your target (and be targeting nothing): /cleartarget
If you turn on sticky targeting, clicking on the ground will no longer clear your target, which is especially great when healing but can leave you targeting mailboxes, vendors, and enemies you aren't fighting, which clutters up your screen and can make using some abilities not do what you want. You can clear your target with the escape key, but that also cancels casting and closes windows.
With ClearTarget, you can make a macro that reads "/cleartarget", drop it on a bar, and use a key to remove your target.
It's about the simplest, shortest addon possible and took about 5 minutes to do while also harvesting thickets, but it's useful for me and might be useful for you.