The Image: Halo's go-to AI character, Cortana, fading away after using the last of her energy to protect Master Chief and briefly appear before him as a hard light hologram. Why It's Powerful: On its own, this is a majestic, mysterious image of a beautiful yet somewhat intangible humanoid: who is she? Why is she all blue? Why is she fading out? And why is she naked? Within the context of Halo, Cortana is one of the series' most crucial and beloved characters, and Cortana's death made Halo 4's ending the most emotional in the history of the series. As well as giving Cortana a heroic send-off, the ending helped to develop Master Chief's character and considering how affected he is by her death, further ensured that he wasn't an emotionless grunt, but rather a believable, developed human being. Could Cortana be back? Absolutely, and we'll almost be surprised if she doesn't return for Halo 5: Guardians, but hopefully she'll be resurrected in a way that doesn't undermine her meaningful demise.