If you want to know about many sandbox features in the soon to be released game, you should listen to this podcast. It's on iTunes too.
This is someones summary but don't take it as gospel. Listen to the podcast.
•Regen field isn't as powerful as Halo 3. If you connect all of your shots on somebody inside of it, they can still die. If you miss, their shields have a chance to go back up.
•Auto Sentry can look 180 degrees. Dies when you die.
•At one point, Auto Sentry used to follow you around. Now it just stays in place.
•Auto Sentry tracks (attacks) holograms
•Holograms appear red on radar at all times and red with reticle.
•Game is faster paced than Reach
•They initially started with the BR and DMR being 4 shot weapons, and but they were ultimately toned down along with the rest of the sandbox across the board to match the traditional pace of past games.
•BR's recoil depends on how fast you fire, but you can learn how to readjust between each trigger pull.
•Aim assist and bloom were toned down on DMR significantly. DMR and BR are vastly different from their previous iterations.
•ALL weapons no longer get knocked out of scope when you're shot at. Instead, your camera 'flinches' while in scope, and this depends on the weapon you are using. The stability mod just controls how bad your camera shakes while you're being shot at.
•Binary rifle has 6 shots total, but only 2 shots before you can reload.
•There's a bright laser for when somebody is zooming in with the binary rifle (like the spartan laser flare from Halo 3).
•"Bi-Ri" has large reticle from the hip and shotgun-like spread, so can't run around 1sk no-scoping unless it's in extreme CQB.
•Armor mods only effect how you play and not who you are as a player. They emphasize that it behaves very differently than how it sounds on paper
•Shield recharge mod recharges your shield ~15% faster than regular, but it still takes 5 seconds out of combat before it will recharge as regular shields do. Doesn't do anything if you're still in combat.
•Nemesis tells you location of person who killed you for a few seconds after you respawn and then goes away.
•Banshee has more health. It had 330 HP in Reach and has 475 HP in Halo 4
•They changed how the vehicles take damage, which they say happens in 'buckets'. Different parts have different health that contribute to its overall HP
•Scorpion Tank's top speed and acceleration are faster. Cannon shells are slower and hdrop over distance.
•All turrets (vehicle and mounted) are more powerful.
•Warthog and Mongoose are sturdier, heavier, and more stable
•Some games have preset loadouts and those will change based on the game's lifespan and rate at which people unlock stuff
•Can only spawn with 1 pulse grenade in loadout (2 with grenadier mod) vs 2 frags or plasmas.
•Pulse grenade has to land on ground before it activates in a sphere. It does constant damage in a few waves and then builds up to explode on a final wave. Can be used for area of denial.
•Binary Rifle, Scattershot, and Incinteration Cannon are the 3 weapons that do the disintegration effect on players.