(A) Unlocking the Halo: Reach Credits and Bonus Terminal Video
Load Halo: Waypoint on your console and press Start and then from the main menu press X to reach the hidden Terminal Access Screen. On the screen are a series of colored discs -- they may be different for everyone, I am not sure about that, but you basically hit the corresponding buttons on your gamepad to match the colors from left to right and you will gain access to a screen with all of the possible symbols from the last part of each of the Terminal CS's in the game.
When you are playing the game, copy the symbols for each terminal and enter them here -- you can find some of these in the videos here, or you can find them on YouTube or you can follow this link to an image of all of the codes: http://last2stand.com/codes.JPG
Accessing the Secret Waypoint Terminal Display
The Secret Waypoint Terminal Display
Change the Forerunner symbols to match those noted from the Terminal videos, then press A, then confirm the code by highlighting the ">>>" symbol, and press A.
Each of these codes, when they are entered successfully, will unlock the corresponding Terminal video in Halo: Waypoint as well as bonus credits.
(01) Pillar of Autumn -- 7,000 Credits Terminal Background 1 Unlocked
(02) Halo -- 7,000 Credits Terminal Background 2 Unlocked
(03) Truth and Reconciliation -- 7,000 Credits Terminal Background 3 Unlocked
(04) The Silent Cartographer -- 7,000 Credits Terminal Background 4 Unlocked
(05) Assault on the Control Room -- 7,000 Credits Terminal Background 5 Unlocked
(06) 343 Guilty Spark -- 7,000 Credits Terminal Background 6 Unlocked
(07) The Library -- 7,000 Credits Terminal Background 7 Unlocked
(08) Two Betrayals -- 7,000 Credits Terminal Background 8 Unlocked
(09) Keyes -- 7,000 Credits Terminal Background 9 Unlocked
(10) The Maw -- 37,000 Credits Terminal Background 10 & 11 Unlocked
When all ten codes are entered the system will unlock the secret eleventh Threshold Terminal Video that can only be viewed in Halo: Waypoint.
(B) Alternate Ending
After you complete the Campaign mode on Legendary difficulty you will unlock an extended ending CS.
(C) Spartan II Linda
In the Cryo-chamber control room (where the tech was killed) there is a set of display panels -- one of which is for you (the Master Chief) and the other of which is for the Spartan II Linda from Red Vs. Blue.
An Internet Meme, Trollface is a black and white drawing of a face with a large mischievous grin that is meant to convey the expression someone makes while trolling a board. The use of the Trollface image in a forum message is generally used to indicate that you believe that someone has been fooled or intentionally angered and is reacting to a Troll.
The Trollface Meme
The Trollface Meme
The face commonly appears in rage comics indicating that the character is being mischievous in some way.
In the level Pillar of Autumn, after you receive the pistol from the Captain, look at the bulletin board on the way out of the bridge and you will see, in addition to the Trollface.