Apologies if this has been posted before without my noticing.
Engineering currently has a number of "Tinkers" that add on-use abilities to items. However, I recently found that contrary to what you'd expect, each item has an independent cooldown; by keeping multiple items with tinkers on them, you can use one every 30 seconds.
Rocket boots:
Use up to 6 per 3 minutes, which is very useful in BGs or just for getting back after a wipe in instances.
Rocket gloves / Hyperspeed:
Doubles the amount you can use in BGs or instances as long as you can get out of combat between fights (an auto-queuing equipment manager helps).
Finally, if not patched, this may become a very nice advantage to the new Mind control helm tinker, which is certain to have a longer cooldown due to its power.