This has been translated from the German gaming magazine "LEVEL":
(Oh, and if you want to be surprised when the game comes out, don't read this.)
"Three Multiplayer levels were tested: Three different multiplayer levels does our own Halo-Fanboy Thomas Wiborgh have time to try out and the levels are limited by invisible walls. If the player reaches to far outside of the level they will be attacked by an automatic defense. Whats the point of it is not presented in the text.
One of the multiplayer level is called "Snowbound". It's a battle level in winter territorie with large Covenant bases. On the levels are also bunkers that are protected by energyshields. These shields can't be penetrated by bullets and grenades, but players can go through it though.
Another level is called "Highground", its shaped for teamplay and reminds of the Halo 2 level "Zanzibar". One team has to defend a base that is on a hill. The other team begins in a beach below the base and has the mission to attack it. In the base you can open alarge gate that lets a warthog from the beach drive inside the base.
The third and last level is called "Valhalla" and is a forest covered level with mountains in the horizon. It's so big that it is made for vehicles and has two large bases placed out. (It's suppose to be the new "Blood Gulch".)
At least two new vehicles A new vehicle has been revealed: "Moongoose". It's smaller and faster then a warthog and has only two places to sit on. It is used primarily for fast transportations. Another vehicle by the name "Man Cannon" has been mentioned, but no further explination has been presented.
Lots of new weapons When it comes to weapon a lot of things has happend. Bungie has listened the critics from Halo 2, that primarily didn't like that it was so important to use two weapons at the same time, so called Dual-wield. Now they have done the standard weapon Assault Rifle a bit more powerful, but it's still not so good as the other weapon in the game.
All the weapon the players carries are being visiulazied in the game. I.e. you can now see an opponent carring around a Shotgun on the back.
Spartan Laser is the name of one of the new weapons. It's made for destroying vehicles and even if it takes time to use and its not so hard to avoid it makes a lot of damage. You dont want your vehicle to be hitted by its red heating ray.
Another new weapon are the Brutes "Spiker". Its like a one-hand Shotgun but shoots out a lot of nails. A new grenade has Bungie also put in. It blows its harvest of nails in one direction and can be placed on walls or the ground.
New Controll The control has some new features: RB and LB (the upper shoulder buttons) are used for reloading the weapons, while RT and LT (the lower shoulder buttons) fires the gun. If you have a weapon in your right hand you reload it with the RB and if you have a weapon in your left hand you reload if with the LB. The X-button is being used for something that is going to "change the whole game", but Bungie are not ready to tell about it yet.
Legendary Edition Bungie are going to release Halo 3 in a "Legendary Edition" that looks like Master Chiefs head. It contains four DVD disc's. One with the game, another with documentaries and commentator tracks, one contains "spinoff-material" like Red VS Blue and Spark of life. And one with all film clips from the game series in a chronological order.
Like the E3-Trailer One game sequence is from the singelplayer part is being showed up too. Accordingly to Wiborgh it reminds of the Halo 2 film that was being shown on E3 2003 and it shows that the game is taking place on earth! This time its going to accordingly from Bungie being directly game parts taken directly from the game."
The ATV is in!!! Whooo!!! Some of this stuff sounds a little off, though. "Man Cannon"? A brute nail gun? Time will tell. Keep in mind, this is translated from German so it doesn't make the greatest of sense.
*UPDATE!*
This site: http://www.videogamesblogger.com/2006/10/27/halo-3-collectors-edition-unveiled-bungie-shows-pictures-of-new-levels-weapons-vehicles-and-talks-multiplayer-and-other-features.htm#more-2802
has scans of the magazine containing the first ever in-game shots. These graphics are by no means final. Expect the finished game to look even better!