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...
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Jerk Store Grunt
We all know of the Food Nipple grunt of Halo:CE, but now there is another. While riding your Warthog through the end of the level, listen to what Cortana is saying. When she says that it is 90% charged, you are getting really close. Once you start heading straight towards it look towards your right. Eventually you'll see a grunt on a small ledge. (You'll have to restart from the last checkpoint as you wont have enough time to go back to your hog) Walk up to it and it will say the soon to be classic line, "Hey demon, the jerk store called, and they're all out of you!" and a few other things. He'll then say that if you don't kill him, he'll shine your boots. He'll shine your helmet. And then eventually say something about not knowing what he's doing half the time becuase of "the gas". Well what are you waiting for, go find him!