Green Smoke Flare

The Green Smoke Flare item is a pyrotechnic device used primarily to mark a location by placing a green smoke column object on the terrain.

Some uses that people have come up with:
 * marking locations for raids
 * smoke bomb the Flag Rooms in the Warsong Gulch battleground
 * props for floor shows and fashion shows

Source
Green Smoke Flares are crafted by Engineers with a skill level of 335.

The schematic for this item is sold for by at the Cenarion Refuge in Zangarmarsh. You must have a friendly reputation with Cenarion Expedition to purchase this schematic. The Green Smoke Flare schematic is bind on pickup, so cannot be bought and sold at the Auction House. Each engineer must purchase their own directly from the vendor.

Green Smoke Flares are also available for 10 in limited quantities by at Area 52 in Netherstorm.

The Green Smoke Flare item does not bind, and can be bought and sold at the Auction House.