Two for One

Two for One is a Halo 3 multiplayer achievement. It is awarded for killing two enemies with one Spartan Laser shot in a ranked free for all playlist (i.e. Lone Wolves). Due to the difficulty in earning this particular achievement, people have been working together to let others earn this achievement. The achievement awards the player 5 Gamerpoints.

It is represented by a white circle with a red star. On top, two skulls and a Spartan Laser.

Method 1
One way to get this achievement is to grab the Spartan Laser on Snowbound under the first base, head towards the back of the cavern which is the main "Arena" that everyone usually flocks to and make sure only the muzzle is sticking out of the energy door shield. Since more than likely all the players will be here and usually only take the tunnel entrances, they'll be too busy fighting each other to notice you charging up your laser from the posterior of the cavern.

Method 2
Another way to get this achievement is to also use the Spartan Laser on King of the Hill gametypes, where everyone will be grouped inside the hill and not able to pay attention to a Laser charging up in the background.

Method 3
One more way is plain and simple and is to have the Spartan Laser on maps that contain Ghosts, and all you would need to do is charge the laser and get the right moment for when someone boards the Ghost, using the Laser to destroy the Ghost will result in the driver and the boarder being "Lasered". Although this can be a quite difficult and time consuming tactic.

Method 4
And of course another way is, to ask somebody to help you with the achievement during a match. Simple (then again, potential interference from the players who are not there to help you can still make it not so simple)! Beware, this is known as Boosting, and can get you banned from Halo 3 by Bungie.

Method 5
In the Double EXP Weekend playlist Legendary Brawl, occasionally there may two players on a Warthog, when you spot it, be quick to destroy them with a Spartan Laser as you're probably not the only one that doesn't have the achievement. (Note: This is only obtainable on Avalanche, Standoff and Rat's Nest, as Ghost Town does not have a Warthog and the Sandtrap variant in the playlist is "FFA Modified".)

Luck!
Sometimes, this achievement is scored by randomized luck and fortune when you try to kill one person and another comes in the way of the other for a close-combat duel. Of course, this is dependent on nothing, but a straight-shot from the Spartan Laser and a great deal of luck. There are also many players in the Legendary Brawl playlist that help each other get this achievement.

Trivia

 * Due to the extreme difficulty of this achievement, it is one of the most common that players usually gather up to help each other get it, which is often considered by a majority of players as cheating.
 * When getting this Achievement, remember it doesn't have to go through both of them, the shot just has to kill two people. So if you can get this Achievement by firing at two enemies standing next to each other.
 * This Achievement may be another seven refence: Two For One=2 4 1, 2+4+1=7.

Related Links

 * Halo 3 Achievements