I hate to say it and I hope Stinkles isn't reading, but killcams would probably convert half my COD friends, as that's one thing they're always complaining about.
I don't want kill cams after every death for these reasons:
1. As someone who plays to win, I don't really care to see exactly how I was killed. All I need to know is what weapon was used to kill me and where it came from. I know all of this 99% of the time in Halo already.
2. I need to be able to rotate the camera around either my dead body or my teammate's body so I can communicate with them and let them know where the enemies are in real time. I can also offer advice based on the situation because I know more about what's going on than my teammates might in that specific moment.
Halo never had this, it doesn't need it and is taking away more important functionality. Keep it in training/beginner playlists, get it out of everything else.