Jdoring
Legend
Well, it's not exactly a default thing, Leveling engineering from 440-450, you'll learn one 'Tinker', There are 8 tinkers, including synapse, 480 Agi/str/int, whichever is highest for 10 seconds, on a 1 minute cooldown, and tazik, a straight-up 3-8k hit on a 2 minute Cd.
People often faction change to a gnome, who can level engineering upto 465 and gain three tinkers, instead of just one, of course you may only get tinkers that require 500+ Engineering skill to use, Cardboard assassin, Invisibility generator, etc.
Edit; Forgot to mention, theres a sticky 'Cata tinkers and you' at the top of the forum, which goes into more detail.
Right i looked at all that but im not sure how important it is, am i going to lose every arena and get globalled constantly in BG's if i dont have synapse or taziks?