Vehicles: Running people over is an instant kill, even on 400% health, look to run over people unless they have a rocket, then keep your distance.
Warthog- All terrain jeep, fairly easy to handle and moves fast, has a powerfull minigun on the back that can kill in a couple of shots, or 1 head shot, holds 1 driver, 1 passenger that can use own weapons, and one gunner. The ultamate vehicle if you have expert gunner and driver, can easily take out ghosts and is okay agianst tanks, good for making flag runs, and hunting down people on foot. The warthog is the best vehicle in the game if two good players are in it it can be unstoppable.
When you are trying to run someone over swing your rearend around, doing a fishtail, this usually helps. When you are trying to avoid being run over by a warthog avoid jumping, and run to the side while shooting at the driver. Not many people know that the "A" button is the break.
Tank- One person is driver and gunner, has a powerfull explosive shot that can take out anything in one shot, good against warthogs or ground troops, also has a machine gun that is only good at close range, up to 4 people can sit on the sides of the tank and shoot, its slow moving so beware of rockets and snipers.
Ghost- 1 person hover vehicle, can strafe which gives it the best handling, same speed as the jeep, has two weak plasma guns on the front kills after about 10 shots, best used for running people over, good for tank killing because the tank can't turn when it gets hit by the plasma guns, good for one person flag operations. Pressing the "A" button while you are moving does a wheely, this is good for dodging tank shots, grenades, and even your own teamates when they get in the way. The "A" button also helps keep the ghost level when you are jumping hills. In blood gultch if you jump the hills on the outside of the bases holding down "A" you can land on top of the base. This is a good ambush spot.
Tank- only the alien ai can use this, fires a plasma mortor that can kill in one hit, slow moving, hopefully its available in halo 1.5 multiplayer
Banshee- only available in the campaign mode, flying spacecraft, fires a missle and has a blasma gun, fast moving, possible contender for halo 1.5