Microsoft Sam on The Covenant
On the level The Covenant after you kill the two Scarabs, get a hornet (If you don't have one)and look straight at the big building in front of you, then move to the right of it and move forward and up a ramp. Then at the top of the ramp get out of your Hornet (be carful that you don't die)then move across the long horizontal pillar that you will see, then go up to the top of a thin ramp infront of you then wait for about 2-3 minutes and then you'll hear Microsoft Sam say a few things... maybe even a thing or two about Marty!
Have a buddy get a gravity hammer. You get a rocket launcher. Shoot the rocket at your buddy, but a little to the side so you don't kill them. Have your buddy swing the hammer. If he times it right, he should hit the rocket and send it in the air.
HEY BATTER BATTER!!
Master Chief's Bullets
When you enter forge you will have an assault rifle. Shoot with it and nothing will happen. Now, exit forge and go to the Theater, then watch your forge video. Pause the video when your bullets are in the air (from your assault rifle that is). Then the bullet should say Master Chief Property.
Song on High Ground
High Ground (Forge)
To find the song, start a forge game on High Ground and go to the room where you normally plant the bomb. If you wait a bit, the radio below one of the computers will begin to play a song that sounds like Halo 2 music ( I have tried to catch the song in theater and have failed. It only appears during real gametime).
Typo in the Credits
This isn't really a glitch, it's more of a typo. In the credits, where it says "thanks" (sorry, I can't remember which thanks it is, b/c there are so many of them). If you watch carefully, you can see it says "7hank you." If you don't watch closely, it'll just blend in, but the "T" is a 7.
Secret Music: Seizure of Madrigal
For those who have played Marathon (I haven't) you may know a song called Seizure of Madrigal. If you know where to look, or specifically, stand, you can listen to this song as much as you want, over and over. On the Level The Covenant you will encounter two Scarbs. Kill them with a Hornet, but don't land yet. Looking at the structure you need to enter at a distance you should see some gray ledges to the upper left. Look for the rectangular ledge that slopes diagonally after a bit. Fly and land there. Now walk up to the end where it just goes straight upward. Stand there, and you'll hear Seizure of Madrigal. If you walk away or wait for it to be over, it will stop. Walk back, it will restart and play. Enjoy the tune!
If you are a fan of Red Vs. Blue, try this. Go to any warthog in the game, and look at the tire. On the tire, you can see the word Puma printed in the side. In Red Vs. Blue, one of the episodes Griff argues with Sarge that the Warthog looks more like a puma.
On the map "Epitaph," if you go to the outside part, you might notice weird birds flying around. Go into the building, get the battle rifle, and shoot them. They will explode and fall to the ground.
Flip an Elephant (Method 2)
During Forge mode, another way you can flip the Elephant is spawn all the explosive barrels in one area. Press "X" on each barrel and change the respawn time to 10 for everyone. Then take the grav lift and drop it under the barrels. The Barrels will respawn almost immediately after blowing up. A continuous explosion meant for having never-ending fun!
Once you have made the continuous explosions, just drive the Elephant over to it, and flip it over!
Red vs Blue
2nd level, Crows nest
In the second level you are going through some caves. You get to a door with a Warthog in a long hallway. The warthog gets blown up, then there's a small battle. After the battle there's a doorway that leads to the hanger, but if you keep going straight the hallway leads to a sloped corner. Around the corner is a soldier knocking on the door with Red vs Blue dialogue. Different difficulties have different dialogues.
Flip an Elephant
On Forge, spawn a Scorpian tank. Try to lodge it inside the Elephant. When you do, move back until the elephant flips. After it flips, it will say "Press RB to flip...wait, what? how did you do that?"