Enigneering woot!!
Feign Death + Jumple Cables = many many people falling in love with you.
Explosives to open doors/chests = many more people falling in love with you
Surestrike Goggles v2.0= me falling in love with myself. lol
Flying mounts(granted they are becoming somewhat commonplace it makes me sad, but oh well)
The Mote extractor. It extracts mote from gas clouds in the air, nothing like flying around Netherstorm looking for mining nodes and getting 7 primal mana within 2 hours. Now if only they would make mote of fire gas clouds I would be very very happy.
Let's not forget the bombs. If your tired of sitting there watching the mage AoE those trash pulls while you already blew your volley load and waiting for the 2 minute CD, you can AoE with those oh so fun bombs engineers make.
But really, it's up to you a few professions offer some really nice stuff for hunters, I just love my engineering and wouldn't give it up for anything.
Edit: forgot something that is great for hunters, you can make your own scopes.
Aside from that don't expect to get rich off of engineering, it really is a self serving profession.
Skinning/ leatherworking is probably the most commonplace and "best" choice because of the really nice epic patterns at 375. Thick Netherscale Breastplate, Nethercobra, Nethercleft, Cobrahide and Clefthoof armor kits are good money makers....
It really just depends on what you want your professions to do, help you with equipment or help you make money or both.
Gathering professions are just for making money obviously so doubling up on one of those is very lucrative.
Engineering makes for a very fun and different playing experience, along with being able to make your own scopes.
Any crafting profession should be taken as either a self serving professions or a money maker, trying to do both will usually result in a net income of zero, not saying you can't make money, but trying to do both doesn't make you much money or you end up taking to much time crafting and not enough time farming mats or advancing in the game.
You can alternate between self serving phases and profiting phases though, but in the end I think you'd be better off just burning through your time and money getting what you want out of the profession(getting to 375 and making your epic patterns) then switching it to profit phase.