Engineers; well you still are not designed as a gold grinder. Enjoy your utility though.
Portable mailboxes, portable banks, teleporters are all things to keep you on the road for longer. Temporary and flimsy crafted tanks can help with levelling - especially for clothies.
But the biggest thing for you this expansion is pet battles. Love it or hate it; Blizzard are aiming for the next generation of players with them. My high school child loves them. My primary school child looks up to them with awe and will work them out.
I already have 'Dad - can you buy for me this pet? What about this one? And this one?'
Engineers - you can make pets; On the topic fishing and archaeology are other very good sources for pets.
Look at your favourite recipe site (http://wow.crafterstome.com/recipes/engineering.html will do), look at the pets and find their sources.
Guns and triggers sell well.
Portable anvils (I could not see if they are bound in any way) will be very popular. I have played the collect from mailbox; run to forge/anvil; run back again, and groan. I am not even a serious blacksmith or miner.
Blizzard really really wants engineers to also be gatherers; with a new pair of goggles to spot additional nodes herb/ore. If you are an engineer with either of those two skills; get the new goggles sooner rather than later.
There are two new mounts; As speculation (because I was not in the mount market at the start of Cataclysm), I don't think that most mount collection will start until the collectors have several alts at lvl 90; but there probably will be a couple of wealthy collectors.
Ganking penalty to save the gankers - One of the things that Albion Online did right was ganking timeout. Gankers lose reputation which they must grind back. If their reputation goes too low, w...
3 hours ago