This is from a thread on Bungie.net.
http://www.bungie.net/Forums/posts.aspx?postID=40433028
- We play as Spartan IIIs. Jorge is the only Spartan II on the team.
- Carter 259 and Kat 320 are the only members of their original squad.
- Jorge is a heavy weapons specialist.
- "Skully" now has a name, Emile 239. He's the silent type of the game.
- The sniper is called Jun 266. He's thoughtful and taciturn.
- We can customise the appearance of the Lone Wolf by a small degree. Awesome.
- The game is apparently darker than any of the other Halo games, even more so than ODST.
- Human Insurrectionists are possibly in the game
- Bungie have once again made the Covenant more dangerous and frightening, as they were in Halo 1.
- Covenant soldiers no longer speak English, they speak in their own languages.
- A new enemy like a Jackal has been introduced, named a "Skirmisher." They are deadly and cunning enemies that attack in packs, and flank secure positions.
- Graphics have been improved drastically, as proven by in-magazine comparisons.
- Elites are back, and are more ferocious than ever.
- Larger scale combat will be in Reach. Where only 20 AI at a time could be on screen in Halo 3, now over 40 AI and 20 vehicles can be present at a time.
- Scenes are more cinematic.
- Noble Team splits up at a point in the story.
- Health Bar is back along with energy shield.
- Single shot rifle like the Halo 2 E3 demo is in the game, named the Designated Marksman Rifle (DRM)
- Sniper, AR and Magnum make a return. Gun sounds are more realistic.
- Needler Rifle is in the game, a mid-range headshot capable weapon.
- Spike Grenades and Flame Grenades are out. Only frags and plasma remain.
- Helicopter Transport is called the Falcon.
- Civillian vehicles are now drivable.
- Fully stealthy gameplay is now possible.
- Assassinations are possible with a knife by holding down the melee button.
- Sprinting is now possible through an equipment like mechanic.
Multiplayer is still 16 players.
Different armor will have influence on you. (armor abilities?)
Lots of customization (they say)
Grunts look different.
Marines look a bit like the halo 1 marines.
Needle rifle confirmed!
Players can change the way the main character looks in campaign.
no spirit dropships. (Still phantoms)
Not much infor here. But 40 AI and 20 vehicles is great news. Battles should be epic.