These were written for the 10fic_10words comm on LJ. The concept is easy. Write a 10 word fic for each genre. All of these are MCxC centered. Reviews are love. :D :D
Round 1
Angst: There was nothing she could do. His luck had run out.
AU: He didn't keep his promise. He lied to her.
Crack!Fic: "Promise me you won't tell anyone about the ballet lessons."
Crossover: "They're not little people. They're Hobbits, Chief."
Friendship: In many ways, she understood him better than himself.
Fluff: "A new matrix chip for me? You shouldn't have, Chief."
Humor: "You had to choose me, didn't you, Cortana?"
Hurt/Comfort: She was corrupted; he only hoped she could be repaired.
Romance: "A feeling stronger than friendship? That sounds like love, John."
UST: Her teasing-yet oddly appealing-smile tantalized him.
Round 2
Angst: She was alone, watching over him in the deafening silence.
AU: "Sorry, Chief, but this installation is mine!" Cortana shouted.
Crack!Fic: Soon, he'd have to explain his pink helmet to her.
Crossover: There, sitting in the Control Room, was a Stargate.
Friendship: He effortlessly kicked away the grenade. "Show off," Cortana grumbled.
Fluff: Their bond was unique; no one could truly understand it.
Humor: "I'd love to have a half-naked AI in my head."
Hurt/Comfort: He was suffering. "Help will be here soon," she promised.
Romance: Nothing, not even a Gravemind, could keep him away.
UST: Her subroutines refused to acknowledge how much he affected her.
Round 3
Angst: As the Gravemind approached, she lost faith in the Chief.
AU: John reluctantly grabbed the Neutral Interface, killing Captain Cortana Keyes.
Crack!Fic: Johnson couldn't believe his eyes. The Chief was line dancing.
Crossover: "You're good, but Samus is a better shot."
Friendship: In the midst of chaos, her voice grounded him.
Fluff: When she entered his mind, she felt at home.
Humor: "Tell me. Do you like the feeling of getting shot?"
Hurt/Comfort: "Stick with me, Chief. We're gonna get out of here."
Romance: John wondered when exactly she became irreplaceable.
UST: Seeing her lean against his helmet was oddly seductive.
Round 4
Angst: He wondered again how he could have left her behind.
AU: Cortana, Spartan-085, nodded to John. She was ready to fight.
Crack!Fic: Cortana played elevator music through his speakers during the mission.
Crossover: "Cortana, can't you just use the Force?" John asked.
Friendship: "Face it, Chief, you're stuck with me." "Well…good."
Fluff: He wondered when Cortana became more important than vengenance.
Humor: "A Spartan, a ODST and a Grunt walk into a bar…"
Hurt/Comfort: Losing consciousness, he knew she would keep him safe.
Romantic: They were alone and lost but neither seemed to mind.
UST: She couldn't touch him, but he still felt her.