I have seen people using different crosshairs on the kill cam.
Unfortunately I can't figure out how to change the crosshair. How do I do it?
After you unlock an attachment with a reticle, such as the reflex sight, you are able to increase its level by using it to get kills. As you advance in level, more reticle options become available.
The attachment doesn't have to be equipped to the same weapon every time for it to gain levels. For example, if you increase the reflex sight's level by having it equipped on a shotgun, it will also be at that level when using a reflex with an assault rifle.
I believe the way to customize the reticle is to have the attachment highlighted (after being selected) and pressing Y (for Xbox).
Press Y(For Xbox) over the sight.
Go to create-a-class then click any gun and put reflex light on if not unlocked try unlock it (really easy to unlock reflex light just keep playing matches) and then click "triangle" on the reflex light and there are your reticles on ps3 its "triangle" on Xbox it's "Y" thanx