Ring of Rockets
From Halopedia, the Halo wiki
On Coagulation (Level), set the game type to just rockets. Then, have some people ride in a Warthog to the hill that is completely covered in shadows. Have one person stay in the warthog and the other people home rockets onto the hog, but instead of firing at the vehicle, fire off to the side a little bit so that you don't hit the warthog. The rocket will keep going in a ring around the warthog. You can fire as many rockets as you want to make a bunch of them circle the vehicle. Eventually, the rockets will disappear. If the person in the warthog is in the passenger seat, he cannot get out until the rockets dissappear or someone else gets in. When you look at the flying rockets you will notice something peculiar. The rocket is aimed directly at the hog but it goes around in circles. Also, if you get into the path of the rocket, it will pass right through you. If the person in the hogs drives away, the rockets will follow him, but they will probably disappear and not hit him. If the person in the hog gets out while he is still parked on him, the rockets will lose their tracking ability and will not hit him.
Why this Works
This phenomenon takes place because a rocket that is homed on something can only take turns that aren't very tight. This causes the rockets to circle the hog if they are shot at the right place. This trick can be preformed with any other vehicle in any other level, as long is it is in a high point so that the rockets do not hit the ground. A good level to try this is with a banshee on Ascension. Fly the banshee into a corner side rail (so it doesn't move) then lock onto the banshee. Then aim above it and shoot. The rockets will become a ring. Move the banshee out of this position to make to rockets follow you.