Alternate Ending Sequence:
     To  see  this  you  have  to  successfully  complete  the game in
campaign  mode on legendary difficulty setting to view a different and
longer ending sequence.

Create more profiles:
     Press Y at the campaign select screen to create a new profile.

Open doors with a ghost:
     To  do  this  park  the  ghost  right near the door, jump out and
quickly jump back in and drive through.

Secret Cave:
     There is a secret cave in level 5 and it is located at the button
of the map entrance. Use it to make an ambush on the enemy.

Plasma Grenade:
     If  your  going to use a plasma grenade, throw it at the alien so
it  sticks  to them. It will surely kill the alien. The aliens however
can do this to you to, if you don't move quickly enough.

Kill a Hunter easier:
     To  kill  a  Hunter easier just get a shotgun and shoot it in the
head.  This  will  cause  it's  head to whiplash backwards and it will
reveal  it's exposed neck. Just shoot it again in the same spot and it
will die.

     Here  is  a  better way to kill a hunter. If you notice they have
orange spots (on their back and neck). Shoot the orange spots and they
will die.

No covenant in Level 5 and finding banshees to fly:
     This  may  take  time  to do, but is WELL worth it. First of all,
this  will  only  work  on Co-op, but does not necessarily require two
people. On Level 5, Assualt on the Control Room, choose any difficulty
(i  found  it  rather  simple  on  easy,  but this code will also make
beating legendary a breeze). Proceed through the level as normal until
you  reach  the  beginning  of the very first bridge. Go down the ramp
which  leads  to  the  platform under the bridge (keep your partner at
side).  When  on  the platform go to the edge and look for the side of
the  mountain.  Jump  and slide against the mountain a few times until
you  find  a  spot  to  land.  After  finding a spot (even if you died
finding it), you are probably dead. So have your partner hit that same
spot  AS YOU ARE DEAD so that you will respawn there when your partner
hits it. He will die but respawn next to you.

     The point is to keep finding edges on the way down to support you
until  you are at a low enough height to land on the bottom. A team of
marines  wait  at  the bottom. You now have access to a jeep which can
take  you  through  the rest of the level without a SINGLE covenant in
sight.  You  will also find A LOT of ghosts, a couple of banshees (one
you  find  after  an  underground tunnel which you have to fly on to a
ridge back towards where the tank is to find the other), the Scorpion,
and  even the covenant tanks which are empty and in perfect condition,
but  you  obviously cannot operate it. If playing to win on legendary,
the level is a peice of cake (you won't get as much glory, however).

     The fun part is getting EVERY single ghost, and the banshees with
the  jeep  and  scorpion  all  together on one spot of land and make a
little parking lot. Fun for a little combat with your friend, also fun
to see all the marines jump in the ghosts and fly around in them.

Deadly as a sidewinder:
Goal: Be an invinceable sniper
     Only  in  multiplayer  on sidewinder with all vehicles and normal
weapons:
     First  you  need  to get a sniper rifle fully loaded. Then you'll
need  a ghost and a warthog. Go up the slope with the small bridge and
rocket  launcher.  Take  the warthog up near the boulder. Get to where
you  are  directly to the right and you're facing the level. Then back
up  at full spead, go up as far as you can and jump out. Now go out to
get your ghost. Get it facing the warthog on the bridge. Go at it full
spead.  Now here is the tricky part. Right before you hit the hood you
need to slam on the breaks but keep moving forward. This will push the
front of the ghost up. If you are successful you will be in a bunch of
nothingness  and be on top of the world. Keep in mind that you'll have
to  grt close to the edge to kill anyone or else the bullets will just
disapear.

For hunters:
     Get  close enough so that they cant shoot but must melee you. Get
right  in front of them, and start running back, they'll chase you and
eventually  swing  their  armored  arm to strike. This will reveal the
orange  flesh.  Shoot  this  and it takes them out easily or when they
swing,  sidestep and pull around behind them. This reveals more orange
skin  on  thier  back,  do  the  same here. One shot kill with pistol,
sniper  rifle,  and  sometimes shotgun. With others, it takes multiple
and you might have to repeat the process several times.

Wanna see a warthog fly high up into the sky?
     Go  to  the silent cartographer, level four. Play co op, beat the
level  without ever using grenades, but dont get into the pelican just
yet.  Drive  on  down  to  the  beach,  somewhere  near  the  bravo 22
crashsite.  Find  two  warthogs, stop near your marines, and drive two
down  to  the  bravo  crashsite. Get out and kill your marines. Repeat
this process until all marines are dead. Now have one player stand and
let  the  other melee him in the back of the head, this will leave his
body  and  grenades.  then the killer should run away so that the dead
can spawn. Now the killed should be the killer and repeat the process.
After  two deaths go back into the level, and find more grenades. Look
at  your  pile  of marines for frags and go back into the facility for
plasmas.  Once you have a large pile of your dead bodies and plenty of
grenades,  drive  a  warthog  over  the  body pile, get out carefully,
wouldn't  want  to  pick  up  any  grenades. Now go and get the rocket
launcher,  fire  a  shot  under  the  warthog  (this  will set off the
grenades)  and watch the car and your pile of bodies fly for miles. If
you  want to try more tricks (getting in the warthog while your friend
sets  them  off  doing multiple warthogs, etc.) simply click start and
then  choose  revert  to  saved.  This  will get you back to your last
checkpoint  where  you  should  still  have  the  pile  of  bodies and
grenades.

Glitch:
     On  the  snow  level  (forward  one), I noticed that you need two
people to do this, when after killing the lot of guys before you would
run towards the generator which would decrese your shield, if you have
two  people  one  can hit the generator, then as quick as possible the
other  person  would teleport the person that which had just generated
the  blue thingy. If you do this right, all the guys should freeze and
you'll  end up behind them watching them frozen. You have two choices,
you  can  throw  grenades  onto  the  guys  or shoot them or whatever.
Unexpectedly, they will stay frozen and so will your grenades. You can
leave  the  exit  behind you and the guys will stay frozen. This cheat
does not work throughout the whole level.

3 gun cheat:
     On  the  first  level,  play either heroic or legendary. Play the
game  as  usual  until  you meet with the captain. Then go to the area
with  covenent  and pick up two guns (any guns except for the pistol.)
Now  go  back  to the bridge until it says checkpoint. Now go back out
and  you  should  see three covenent standing just outside the bridge.
From  here on, you should have three guns. It can only be used on this
stage.

Fireworks:
     You  can make your own fireworks in Halo. All you need to have is
2  plasma  grenades.  Make sure you outdoors, I find the cartografer a
good  lvl to do this or you can just do multi-player. Simply throw one
plasma grenade and then throw the 2nd on the same spot. The first will
explode  sending  the  second  up  in  the air and then the second one
explodes  a  few  seconds later. This doesnt really effect the game in
any way its just kinda fun to watch.

Fun thing to do:
     In  the  first  level, after you get the gun from the captain, go
outside and kill the grunts after. When you get some grenades, go back
to  the  captain  but  don't  go  pass  the checkpoint or else it will
activate  it. Then throw all your grenades in there and hopefully some
people  will  die.  THEN  START  RUNNING  LIKE HELL!! A whole bunch of
marines will come after you and you can have some fun!

5th level tip:
     On the 5th level, (First snow one, Asult on the Control Room) you
can  save  a  lot  of time by stealing a banshee from the unsuspecting
covenant. To do this all you need to do is go out to the first bridge,
(A  snowy  one  I  think...  Only 1 snowy 1) run straight out into the
battle,  throw  a  nade of any type (Prefer the plasma) to the area in
which  you  enter  the plane (which should be straight ahead) jump off
the  right  side  off  the  cliff,  keep  pressing (X) or your default
Reload/Action  button  while  you  are  jumping TORWARDS the plane. (I
think  you  dont  have  to  jump  off but its hella cool and fun to do
anyway!)  then just fly torwards the end of the map after killing some
guys  for  fun  (End  of  map is the huge door that opens and you have
completed half the map in a hella short time!