Vidmaster Challenge: Déjà Vu

Vidmaster Challenge: Déjà Vu is an achievement in Halo 3: ODST and one of the Vidmaster Challenges. It is unlocked when you complete Coastal Highway on 4-player Legendary Live co-op, with Iron skull activated, and not using the Warthog or Scorpion at all, but Ghosts, Mongooses, and Wraiths are allowed. It is worth 25 Gamerscore.

It is represented by a green Marathon symbol, with the Iron Skull in front of it and two white stars on both sides of the Iron Skull.

Strategies and Tips

 * At the beginning of the Highway, there is a tunnel that leads underground. You will find four Rocket Launchers, with 1,000 rockets (2 loaded in the Rocket and 998 on reserve), and two Mongooses. These only appear by putting the Iron Skull on Legendary.
 * The Rocket Launchers mentioned above have special properties, allowing you to carry a rocket launcher from the first part of the level and the 1,000 rocket version, implying that these were specially made to make this very difficult achievement easier.
 * If there are Banshees, try to get off your Mongoose and destroy them when they move to you.
 * Try to stay behind the Elephant.
 * Don't rush the level; try to stay back and destroy the Type-32 Ghosts and Banshees before moving in.
 * A charged Plasma pistol will help you hijack Ghosts if you're close enough. Be careful if you attempt this as the EMP does not disable weapon systems.
 * Try hijacking an, it may take some time, but is worth it due to its high rate of fire and increased damage.
 * If you are having a problem getting a checkpoint when you open the gates of each section, make sure that: Everyone is close to each other and in the gate at the same time; You are not shooting at any Covenant and they are not shooting at you and Dare's Olifant has not moved completely out of the gate. A Cooperative checkpoint is not the same as a normal Checkpoint (Cooperative Checkpoints are where you start the level from if you save/quit).
 * Grab a health pack and regroup at each checkpoint. If your Mongoose is heavily damaged, grab a new one that sometimes appear in each checkpoint.
 * Although walking the whole level is near impossible, if you find yourself stuck on a certain part, try getting off your Mongooses or Ghosts and start walking. It is easier to aim, easier to see, harder to be hit, and you will have twice the number of rocket launchers firing. As long as you can deal with threats to the Elephant quickly, walking the section is a valid option until it is completed.
 * For the passage containing all of the Drones (the 2nd or 3rd), it is helpful to keep the SMG to deal with them, as hitting them with rockets can be quite difficult.
 * Make sure that all your teammates are using their headsets for easier communication over Xbox Live.
 * Buck will follow you, but if you find a Rocket Launcher, or, even better, a Fuel Rod Cannon, and equip Buck with it, he is a very powerful ally. If he rides on a Mongoose with you, he is very helpful at taking out Ghosts and Banshees. A Fuel Rod Cannon can be found on a dead Grunt, after your first battle on the highway right before the first door.
 * If you cannot get a fourth player then you can add on a guest and still be able to get the achievement.
 * When a group of Phantoms carrying two Ghosts was on their way to the next section, open fire to the gunner to destroy its main cannon and belly section. Force the Phantoms to drop the Ghosts, so you would have less resistance on the next section (Which contains only two Shade Turrets).
 * If you manage to seize AA-Wraith, it would be better since it can destroy the Phantom faster.
 * The lesser ghosts dealt with in the next section, the better.
 * Try not to drop the Ghosts on the highway, since the Ghosts would begin pursuing players in earnest.

Trivia

 * The achievement is named due to the similarity to another Vidmaster Challenge achievement: Annual, which also requires the Iron Skull, 4 player Legendary live co-op play, and finishing in a light vehicle (as walking is not suggested due to the Elephant being faster, and on legendary can be destroyed in a matter of seconds from enemies) on the last level.
 * Rock Anthem for Saving the World from the Halo: Original Soundtrack plays when you walk down the first off-ramp where the Mongoose and Rocket Launchers are located.
 * Déjà vu is French for already seen and means having a familiar feeling; as if you'd have already been to a new situation previously. This is a reference to the Vidmaster Challenge: Annual, which has similar requirements.