Turf vacation

From Halopedia, the Halo wiki

You can get beyond the gate in Turf

(This requires two people and over shields) First, have one player stand in front of the gate, and the other in a warthog, have the second player ram into the first player, if done right, the first player should be propelled through the gate.

There are two ways to get beyond the barrier and roam outside the map. One can be done by one player alone.

To get out of the map with just one player, head over to the medical tent area. Get on to one of the ledges on either side of the tent, that are a little above the top of tent. From here, locate an area on top of the tent where there are six little "dots" in the metalwork. Jump onto those. When you are in the middle of this jump, hold crouch, and right before you land let go of crouch. There are two pairs of these six dots, and it works much better jumping the dots closer to the side the Warthog and shotgun spawn area. After you have perfected the jump, perform it again and land on the building on the edge of the map with several windows with windowsills and shutters overhanging them. Be sure to be crouching in the air after the jump, when you land, and stay crouched. If you are facing the building, land to the right side or edge of it. Then, crouchwalk to the left side, facing slightly to your right. If done correctly, you will slip out of the map. It is also easier to perform the superjump if you jump onto the tent from the side this building is on. Remember, like with all glitches of this nature, it is very hard to perform them the first time, but they gradually become second nature. Don't get discouraged.

Alternatively, you can use two people to get out of the map. This method cannot be used in matchmaking, however, the exception being Team fiesta within Team Training, as you need two players with swords. Have one player go behind the medical tent area where you can use a crate to jump up to a ledge where a Plasma Pistol rests. Instead of this ledge, go to the one just across the ramp you use to get up to this area. It looks identical to the Plasma Pistol ledge. On this ledge, if you look, you will notice a bit of wall coming out of the side nearest the edge of the map on the floor of the ledge. Use this as a ramp of sorts and walk as high as you can. Now, with some effort, you can crouchjump onto the orange overhang just to your left and above you. Once you get up there, face toward the medical tent area and you'll notice you can jump onto the gray concrete wall. Carefully worm around this wall until you can see in front of you the building with the windows and overhangs you use to get out alone. Have this person stay here. The second person's job is slightly more difficult.

Go to the medical tent area and jump onto the windowsill on that same windowed building. There is only one window with a windowsill that you can jump on because it is the only one lacking an over hang to knock you off. If you turn left from here, you'll notice a window with an overhang you can jump onto. Jump onto that overhang. Now, notice the parapet-ridden wall that makes one of the map's barriers. Perform a late jump off of the overhang to get on top of it. A late jump is jumping when you walked or ran off a platform but jump just soon enough to jump off its edge. It needs to be late so you do not hit the ceiling above. Once you get onto the parapetted building, walk along it towards the area the other player is at. This is the hardest part of the glitch coming up now. Be very careful. You will have to perform a crouchjump onto the metal rails on the side of the wall opposite the windowed building. You will fall off if you just stand there, but if you jump quickly enough, you can jump again onto the slanted top of the wall.

The two players should now be facing each other. This is where your swords will come into play. You will want to sword cancel off of each other. This will eventually break through the barrier. To sword cancel, just press R (RT if you are on a 360) and X simultaneously. This will make you do the traditional sword lunge, but cancel the actual attacking phase itself. You will notice when you break through the barrier. You can roam inside the area you formerly were stopped from going to by the invisible wall. Now the first person who got through should just stand there until the second person gets through the barrier by the same method. Now look to the high wall on the side of the area you broke into. Have a person jump at the side of the wall and the sword cancel while they are airborne. This will land you on top of that wall and you can roam around the massive outskirts of Turf. If you miss the wall and go past, do not fret. Look back towards the medical tent area and you'll notice that same slanted roof the second player had to jump to. With a well-placed crouch jump, you can jump to it and get on top of the wall.