Alternate ending sequence
Successfully complete the last level of the game in campaign mode under the legendary difficulty setting. The new ending features a human and alien fighting hand to hand. The human will say “Its over”, and then they hug because they know the explosion will kill them both.
Defeating Flugs
In the later levels of the game you will encounter new enemies called Flugs. These enemies will be small at first, but they will attack and control anything alive. Use a shotgun on these baby Flug as they tend to group in large numbers. By using the shotgun it will send a storm of bullets and kill most of them that are around. Use a shotgun on the possessed Flug, and it will kill most of them in one shot. This is made easier by the fact that most of them carry shotguns.
Defeating Grunts
When the Grunts are sleeping you can beat them to death with the butt of your gun without waking up any of the other Grunts. You can usually kill a four to seven of them before an alien spots you. They start sleeping in level 5, Assault on the Control Room. Just remember not to shoot or they will wake up.
Defeating Jackels
Use a photon weapon to destroy a Jackel’s shield quickly. When you encounter a Jackel, run up and hit it with your weapon or get out a gun that uses bullets, not energy.
Covenant dropship
When Covenant dropship is getting ready to unload a group of Covenants, throw a grenade into the door as it opens. The blast will kill several of the enemies since they are all in one area.
Assault On The Control Room: Spinning ring
At the Halo start up screen, choose multiplayer mode. Choose cooperative play at the next screen, then choose your profiles at the next. Choose the level where in the beginning it says, “I would have been your daddy” (Assault On The Control Room). On the difficulty screen, choose legendary. When the level starts after the introduction sequence, have one of the players quickly press X when the “Press X to get on the Pelican” message appears. That player will re-board the ship and start flying with it down the hole. The other player will quickly die because of the aliens, and will be respawned on the spinning ring. Make sure to jump where there are gaps. If you are good enough, you can even jump to a nearby ledge. Additionally, once you are respawned on the ring, quickly jump off and fall to your death. Sometimes you will be respawned on the lowest ledge in all the blue haze, and a “Press X to flip the Pelican” will appear that the top of the screen very briefly.
Unlock New Guns
To unlock two new guns, first beat the game on the easiest setting (Easy), and then on the hardest setting (Legendary) in under 3 hours.
Fireworks
Through one plasma grenade in a wide open spot, then stick another directly on top of it if you do this fast enough the first gernade will launch the second and vuaola fireworks.
Your in My Seat
When one of your computer controlled buddies is in a vehicle spot/seat you want simply go over to that spot and press X. They will graciously move.
Infinite Grenades
To get infinite grenades, scorpion, and ghost in multiplayer- Go to the multiplayer screen: go to edit game types: In that menu you will have the option to make up your own game type.
Shortcut
Play “Assault on the Control Room”. It doesn’t matter what difficulty setting or if you are playing 1 or 2 player mode. Get to “If I only had a super weapon”. Rush right ahead and ignore the Jackals and the first Elite. Instead, kill the second one as he is somind over the hill. Then run to the next one who is coming around the banshee. If you kill them both, the two banshees will be yours for the taking. I would suggest using the Plasma Rifle for killing them, as it stuns. You can use the 2 banshees for a banshee fight with a friend, too. Anyways. Ignore the enemies and do not go to the end of the bridge. Instead, go to the top of the hill that leads to the Control Room. There will be no Hunters, or aliens on the way up the hill! There will be the enemies that come out of the big door, though, but this shave’s precious time off the level.
How to get a Banshee sooner than the bridge
Assault on the control room: How to get a Banshee sooner than the bridge, 1 player.
Fight your way through the level to the first snowy open area, kill the enemy tank and all the rest of your enemies then hop into the Warthog. Make sure you get the Rocket Launcher and the Sniper Rifle. The next open area has a battle raging and an empty Scorpion, hop into the Scorpion and waste all the Covenant with the cannon. To the left is tunnel, to the right is the obvious way to the next open area, go to the right and clear the enemies around the corner. Stop (If you kill all the enemies in the next open area an Elite will get the Banshee before you do and use it to attack you. You’ll know you’re in the right place if there’s another enemy tank in the area.) Now, jump out of the Scorpion and stay to the Left edge of the valley. Look up, you should see a Ledge above you with some lights on the underside. The Banshee is on that ledge so get underneath it and shoot some rockets up to knock it off. Remember to move something forward with concussion weapons you have to shoot behind it, so use you brain. If done correctly off will tumble the Banshee, if done incorrectly it will be pushed farther in. As an added bonus the last few sections of the level will have no enemies due to the fact you’ve skipped so much.
Plasma Grenade
If your going to use a plasma grenade, try throwing the grenade on the alien where it sticks onto them. It will blow up on them making sure it will kill the alien. Also the aliens can do this to you if you don’t move.
Name in Blood
In the very last level of the game, as you’re driving the Warthog out of the Pillar of Autumn, on the second jump, do not go all the way across. Then back into the room thats behind you and get out. if you look on the wall the name REX will be in blood on the wall.
Hungry Grunt
In the very last level of the game, as you’re driving the Warthog out of the Pillar of Autumn, get out at the 2 tunnel off of the main one and there will be a grunt at the end of it. he should say something like ” I can’t wait to get back to the ship and eat some grub!”
Good tactic for legendary
Here’s a good way of killing elites or hunters in legendary. get a needler and some ammo and just unload it on an elite and watch the show –NOTE– You have to get in close enough for the needles to find their mark, and the delay until they explode leaves you wide open for their plasma rifle, so bring a backup weapon.