Here is an interesting comparison of Cortana over the course of the 4 halo games:
PTesh adds his dulcet prepubescent tones over the top of one of the new trailers for weapons...
Try upgrading your browser to Google chrome (you wont regret it). There is probably an IE...
Level: Oni: Sword Base
On Mission 03, Oni: Sword Base, there are two hidden switches, marked as "doors" that you can open only with two players in a co-op match. Both switches can be found after Rally Point Alpha, where you must destroy the Wraiths. Switch A is found on the coast of the water just southeast of the buildings with a pair switches you must activate. It's on a pile of rocks near the frozen waterfall. You'll know you are standing in the right place when you get a message saying "Hold X to Open Door." Note: You must reload your weapon before getting this. Switch B is just past the AA cannon in the next area. A pile of rocks with some trees on it overlooks the vast, walled complex on the ice below the area. With both people standing in these places, press X simultaneously and a message will appear on screen saying "REACH RACER." You will then be warped to the Oni: Sword Base with two Gauss Cannon Wart Hogs ready for racing. You can race your friend through a course marked by red waypoints (you don't need to touch the waypoints, you just need to cruise past them). At the end of the race, the loser's Wart Hog explodes and you'll both be warped back to race again.