I know this has been posted before in another section but I think it would be nice to be stickied here as BG/PvP is the main use for it.
There are many ways to use this, and I'll explain them after we set this up.
1. When in-game, press Esc on your keyboard and click the Macros button.
2. Create a new macro, and in the text, type /sit, then press enter, then type /stand, then press enter and repeat that process until you run out of space.
3. Save the macro, and move it somewhere on your combat bar.
The way this works is that you spam the macro while moving in any direction. It will freeze your screen and you will appear to move in the same direction you were moving when you started pressing the button to every character around you, but in all actuality you will be standing still. If you do this for more than around 10 seconds you could be disconnected, but that's plenty of time.
While moving, melee characters can't hit you as you're not actually there and ranged can't hit ya if they're not facing you
Strategies: World PvP
This is very good for getting away from players. If you spam it while moving towards a cliff or off a zeppelin or boat, you will appear to go off it but you will actually still be on. If the character wants the kill he will most likely "follow" you off and you would be safe.
Strategies: BG
This is pretty useful for flag carrying. When you are being chased with the flag, spam it in a different direction than you actually want to go, then when you stop spamming go where you actually want to.
You will keep lagging for as long as you press it. If anyone has more tips/strategies, please post them and I'll add them to here and credit you. Thanks for reading.
Edit: Also, if you are being chased by someone on a mount, you can spam it while moving towards water and if they follow you in they will be dismounted while you remain on land. This could apply to world or bg so I didn't put it in either.