Hold down left trigger and then press the right bumper. Or hold the right trigger and press the left bumper. You will cycle through enemies, and enemies only. This is remarkably useful as a tank, especially a gladiator tank. With all of your attack macros set to the right trigger, you can hold the trigger down, use an attack on one target, tap the bumper to switch targets, use a combo action to build enmity on the second target, and cycle as needed (unless you have party members that can sleep).
Also, for those that don't know... you can dismount your chocobo by merely pressing in on the left analog stick.
I ended up removing my old shield lob macro in favor of having fast blade and shield lob on one macro. It's a simple two line macro:
/ac "Fast Blade" <t>
/ac "Shield Lob" <t>
It's a simple, yet useful macro because if your current target is outside your melee range, fast blade will fail to execute and shield lob will happen instead. If you are in range, fast blade will execute and shield lob will not because fast blade will have activated your global cooldown.
Edit: Oh yeah, if you choose to use that macro, make sure to turn off error messages in your chat channel or you'll see them constantly.