Used Car Salesman

Used Car Salesman is a Halo 3 Achievement. It is awarded for destroying a vehicle with three enemies in it in either a ranked online playlist or in campaign. Unlocking this Achievement gives you the Scout Helmet for Spartan Armor customization. It is represented by an eight-pointed yellow star on top of an eight-pointed red star. On top of this are three white stars.

Method 1
The easiest way to get this achievement is on The Covenant, after you disable the Third Tower and are on your way to the Citadel (load "Rally Point Bravo"). Get in the Scorpion tank, and destroy the Prowler that comes around the corner. Alternatively, you can steal rockets from the guy on the Mongoose riding along-side the Scorpion tank and weaken the Prowler with your assault rifle before destroying it with rockets.

Method 2
The best way to get this achievement is by playing on The Ark. Get to the bit with the crashed Pelican there will be a Rocket Launcher. Once you have killed off the Brutes, two Prowlers will come your way, hopefully one of them will have three Brutes on it. Do not fire the Rocket Launcher straight away as it will only kill the Brutes but not the Prowler itself and will not count towards the achievement. Try shooting it with a smaller fire arm then finish it with the Rocket Launcher, that way the vehicle will be destroyed. An easier way is in the hanger of Crow's Nest. Two Phantoms come inside the hanger, three if playing on Heroic and Legendary. There are two turrets in the area, or you can run up and stick the turret with a plasma grenade (spike grenades aren't strong enough to blow the turret to pieces). You can also wait until after Forward Unto Dawn drops off the three Scorpions and the Gauss Warthog. There are multiple opportunities where a Phantom is stationary and in range. Using the Scorpion's primary weapon, roughly 5-7 direct hits will shoot it down. Another simple tactic would be to use a Spartan laser against a Prowler, of course with a well aimed shot.

Method 3
On the level The Covenant, save your Spartan Laser energy until you get to the Wraith guarding the tower. Take a Ghost and drive up the naturally formed ramp to get to the platform in front of the Shade Turret. Kill the Wraith as soon as possible! Also, a few Ghosts with Grunts driving them roam the area so wipe them out with the Warthog. Eventually two Prowlers come out and both have at least three Brutes in them and you should be able to wipe it out with a well placed Spartan Laser shot. There are more Prowlers in the Assault on the Citadel part later in the level so if you fail at the first tower, use the Scorpion to knock out the Prowlers there.

Method 4
The actual easiest way to get this achievement is on the level Crow's Nest, when the Phantoms in the hangar drop off Covenant infantry, you can use the Machine gun Turret to destroy the Phantom's Plasma Turret(The front of the dropship), or stick a Plasma Grenade on it. Once the turret explodes, you should get the Used Car Salesman achievement, even if there are no Brutes in the dropship. If the Turret explodes and you don't have it then keep blasting the belly of the ship and you should get it.(This is a Glitch)

Note

 * Another simple method is on Sierra 117 after you've rescued Sergeant Johnson, just stay in the building until the Phantoms arrive and throw a plasma grenade at the front turret.
 * Another method involves simply using the Spartan Laser while in Matchmaking to destroy a warthog with three passengers, common on Capture the Flag variants.
 * An easy way to get this achievement is on Tsavo Highway on any difficulty when you get the Warthogs at the start of the level. First you drive towards the part where you see the phantom dropping off more enemies and shoot at the front gun, and once it breaks off you should get the achievement.

Related Links

 * Halo 3 Achievements