Cortana is one of the most popular and important characters in the Halo franchise. In fact, she has even transcended the games at this point by becoming Microsoft's personal assistant AI, meaning that more people probably know about her than Master Chief.
Cortana has maintained a lot of popularity, even despite becoming a villain in Halo 5. Cortana has also had a lot of interesting things to say, especially in the earlier games when Master Chief didn't talk. So this list puts together some of the most memorable quotes of hers.
10 "Don't make a girl a promise... if you know you can't keep it."
One of the most iconic lines in the Halo series and a solid piece of advice for anyone. This quote is heard multiple times in the series. The first time it is said, it is as the parting words between Cortana and Master Chief in Halo 2, as a response to when Chief tells Cortana that he will return to her after dealing with the Prophet of Truth.
It is later her again in Halo 3 when Chief is having one of many "Cortana Moments," The phrase is also said by Doctor Catherine Hasley in Halo: Legends.
9 "Chief, when you get to Earth, good luck."
Said at a similar time to the last quote. In fact, it comes right before it. This is said just ahead of Chief going off to try to board the Forerunner Dreadnought.
This is a good quote because Cortana knows that there is a decent chance of her not surviving the events that were about to happen and even if she did, there was a solid chance that she would never get to see John again.
8 "It's been an honor serving with you, John."
This quote is said at the finale of Halo 3. After Arbiter and Master Chief have made it onto the Forward Unto Dawn and they are trying to escape from the explosion caused by destroying the Halo ring. Cortana in unsure about their chances of being able to escape the blast, but the Chief is confident, reassuring Cortana that they are going to make it.
This quote is said just to let Chief know that Cortana has enjoyed their time together, no matter how dangerous it was.
7 "Wake up, Chief. I need you."
This is one of the lines said by Cortana in the opening scene of Halo 4, as well as in the trailer for it. This is the first line that she says, which is a distress call as the section of the Forward Unto Dawn that they are in is under attack.
Chief is still asleep in one of the pods on that section of the ship and it has been two years since the end of Halo 3. This is not only a good line for the situation they are in but also a good one to reintroduce fans to the world of Halo and the story of Master Chief.
6 "I'm just my mother's shadow... don't look at me, don't listen! I'm not who I used to be..."
This is another one of the Cortana moments that chief has in Halo 3 throughout the game's various missions on the lead up to actually finding and saving her. There are a lot of these as you don't find Cortana until one of the last missions.
These moments get more and more depressing as the player advances throughout the game. This quote is in reference to Cortana's creator, Dr. Catherine Halsey, and the trauma that she is being put through at the hand of the Gravemind.
5 "Could you sacrifice me to complete your mission? Could you watch me die?"
This quote comes from one of the earlier Cortana moments that Master Chief has in Halo 3. This one appears in the level Sierra 117 and is one of the first to happen. Cortana moments are followed by Chief having visions of Cortana as well like she is a ghost haunting him.
Canonically, this is first said by Catherine Hasley, at least chronologically, to Chief before an operation known as Operation: RED FLAG in Halo 2.
4 "I am your shield... I am your sword."
Cortana moments have some of her best quotes, mainly because Cortana's main job for most of the games is to spit out exposition when she is with the Chief and the Cortana moments give her a time to shine. That being said, this quote comes from a Cortana moment in the level The Storm.
This quote is less depressing and ominous as it comes in an earlier mission in Halo 3, implying that Cortana still has a sense of her own sanity and has not yet been broken.
3 "I was put into service eight years ago. AIs deteriorate after seven, Chief."
This is one of the first lines that Cortana says in Halo 4 after she and Master Chief land on Requiem after the section of the Forward Unto Dawn that they were on was destroyed. This quote is said after Cortana starts to show the early onset symptoms of Rampancy and Chief questions her about what is going wrong with her.
This is sad as not only does it imply that Chief doesn't know much about the lifespan of AI but that he is going to lose the person he is closest to soon.
2 "Welcome home, John."
This quote hits hard to a lot of fans, especially when they first heard it when they were going through their first playthrough of Halo 4, especially since fans wouldn't know what was going to happen in Halo 5.
When Cortana says this, she and Master Chief had just defeated the Didact, using Cortana's Rampancy to their advantage. Unfortunately, this means that Cortana had to sacrifice herself and say goodbye to Master Chief, with this being the last words she said.
1 "I'm not doing this for mankind."
Sticking with the same period of time from the previous quote, this is said in the final cutscene between Master Chief and the Didact. After uploading Cortana into all the terminals but having her upload chip destroyed in the last one, Chief has his final stand against Didact.
Right when it looks like Didact is getting the upper hand, Cortana uses the multiple copies of herself to take down the Didact who questions why she does so much for humanity. This quote is her response, showing how much she cares for John.