In addition to what Josh Petrie mentioned: if you're looking for more advanced ways to aim weapons, the center dot in your bottom image is also called a "pipper" in real-life applications.
This especially applies when some device is actively predicting where an arcing projectile will impact, like a bomb or grenade, instead of simply showing which direction it will go when fired/thrown/dropped.
Aircraft HUDs combine pippers and reticles to convey extra information about complicated firing solutions. So in your third image, the circular arcs are the reticle, while the center dot is the pipper.
