Halo: Combat Evolved Cheats

Sniping technique
Here's a cheap sniping tactic to aggravate your friends with next time your in a deathmatch. Turn on all vehicles, weapons on normal, and play on the sidewinder level. Grab a sniper rifle and a tank, drive it up to the outer cliff on the blue light side where the rocket launcher is located, drive the tank around the cliff past the rocket launcher towards the outside of the portal. Now back it up the hill next to the portals outside door, the tank should be facing straight at the tree out in the middle of the level. Soon as it's been back up that it cant go any farther (enough that you could get under it) go get a ghost and go off the tank like a ramp. This is a very stressing trick, it will take a while but you'll know you have gotten in the sniping spot when you fly off the tank out beyond the boundaries of the level. Now you can walk around the whole level and pop out whenever you want and snipe your friends and then pop back out so they cant hit you. (it looks like your flying and sometimes you can keep the ghost up there).

Easy Way to Kill an Elite
It's simple, if you have a plasma pistol charge it up and fire it at an elite (if it tries to dodge it, the shot will follow it) and that should take out its shield, then pull out any other weapon (assault rifle works best) and waste em!

Good tactic for legendary
Get a needler and some ammo and just unload it on an elite and watch the show --NOTE-- You have to get in close enough for the needles to find their mark, and the delay until they explode leaves you wide open for their plasma rifle, so bring a backup weapon. For the hunters, unload an entire clip at their backs so the shot doesn't reflect off their shield and start shooting at them with another weapon while waiting for the needles to explode (or just sneak up on one and smack him in the back, and if you cant to that...a well placed plasma grenade to the head should weaken it, but it will most likely just piss it off.)

Having Some 'FUN' With Hunters
It is like playing with a bull (a bull with a fuel-rod gun and a bad attitude) with a red flag. Wait for it to melee you and right before it hits you move out of the way and hit it in the back. Then jump out of the way so it doesnt kill you. This trick is very hard to do however, try and get behind one hunter so the other one shoots at you and hits the other one in the side...or head..or wherever it might hit it. i did this once and it killed the hunter.

Plasma Grenade
If you're going to use a plasma grenade, try throwing the grenade on the alien where it sticks onto them. It will blow up on them making sure it will kill the alien. Also the aliens can do this to you if you don't move.

Driving Warthogs in Halo
When driving a warthog before you drive off a cliff spin right away to the side and the warthog won't tip but will stay horizontal and land from and height,(this won't work if the cliff goes off that certain level). Also, when turning to make a perfect turn, only do lots of little movements on the right thumb stick. Do this so that the warthog doesn't skid out from big turns and you can control it better.

Secret Cave
There is in level 5 a secret cave at the button of the map entrance. It comes out on the side where they are not expecting a side attack from that side and it shall be easier.

Get New Ending Sequence
Finish the game using legendary difficulty setting in Campaign Mode.

Shoot enemy through wall
This is a glitch, not a Halo cheat. In multi-player mode, drive any Warthog close to a building so that the side of it is touching. Get in the gunners turret and turn it towards the wall. If done correctly and you are close enough, you should be able to to shoot at an enemy through the wall and not receive damage from them if they shoot back.