Mekgineer's Chopper

Mekgineer's Chopper is a chopper vehicle created by top Alliance engineers. This vehicle allows one party member to ride along in the sidecar. It's one of the few mounts that can be bought on the Auction house, however it will usually cost plenty of gold, considering the price of the mats to create it.

Mount Journal
Sporting superb engineering craftsmanship, this chopper is one of the few personal vehicles on Azeroth built for two.

Activating the sidecar
To activate Mekgineer's Chopper's sidecar and carry a passenger, simply invite the player to a group. The player's pointer will turn into a green mounting arrow when they mouse over Mekgineer's Chopper, allowing them to jump on while the sidecar deploys itself automatically. Note that if you are in a raid group, your passenger must be in the same group (1, 2, 3...etc) as you to enter the side car.

Source
This item is crafted with Engineering (450); taught by Schematic: Mekgineer's Chopper, an Alliance Vanguard reputation reward.

This mount also has an extremely rare chance to drop from the Blingtron 4000 Gift Package and Blingtron 5000 Gift Package for Alliance characters.

Trivia

 * The vehicle comes with a license plate with the word "" on it.
 * A Mekgineer's Chopper can be found outside Like Clockwork in the Magus Commerce Exchange district of Dalaran.
 * If the driver enters a phased area that is different to the passenger's phase, then the passenger phases out but the sidecar remains deployed. The passenger sees the driver, though. If either dismount in a differently phased area, the driver sees the passenger briefly appear, then both phase out on each other's screens.

Achievements
Obtaining this mount rewards the achievement Get to the Choppa!.