These are some of the Strategies that I used to beat legendary and that I use in multiplayer
Single Player
Marine Meatshield
-Weapons
-Enemies
-Allies
I found this trick especially useful on Level 3 when taking the gravity lift, you stand back and snipe at things when you let all your marines die. This didn't work to well on the first room in the ship on level 3(Just after you go up grav. lift) as they come form everywhere.
-Strategies
-Glitches
-Halo 2
Sleeping Grunts
When you see a sleeping grunt is means that an elite or multipule elites are nearby, some people will take on all of these guys, if you kill of the elites quietly(no shooting allowed even by the elite), or don't get seen by then at all, you can bypass the room with no lost health or ammo. This can allow you to skip 3-4 Rooms on AOTCR
Color Coded Elites
This really isn't a stratagy but I have nowhere else to put it, There are four colors of elites, Red, Purple, Gold, and White. Each of these colors have a different ranks and tactics.
Red andPurple - These guys don't do things that differently, they are the basic elites of the covenant and only really use thier guns, no grenades that much.
Gold - I only found these guys on levels that the covenant where defending something like AOTCR, they and the white ones are the only ones to use Swords, I've never really fought with these guys so i don't know thier tactics that much
White - These are the Covenant strike teams found in the later levels of the game, they like using grenades some times on you, other than that they basiclly fight like the Red or Purple guys
Skipping Parts
These are very usefull if your low on health, but after beating it like this I like to go back and beat it normal so I can say i beat legendary fully. There are some parts you can skip about half of the level, like in SC with the Second shaft, using a hog i skipped the trip down(I had 1 red bar of health after getting down the fast way though).
Hijacking
On AOTCR(Maybe 1 other level) you can steal a banshee that Bungie didn't intend for you to get, you will most likely need invisiblity or possibly a tank to get it though.
NOTE: I will tell you how to get a banshee on AOCTR in my glitches page
Multi Player
Piliage powerups
This can only be done on rat race, if you shoot the powerups that are floating in the air they will fall to the ground and you can pick them up with running around to get them.
I dont really use any tricks in multi player I just like to grab a Sniper Rifle and a Pistol, find a good sniper spot and camp there till my opponent can get me out of there.
Sometimes i use the invisibility + Rocket Launcher combo on Hang em high.
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