There is in level 5 a secret cave at the button of the map entrance. It comes out on the side where they are not expecting a side attack from that side and it shall be easier.
Get New Ending Sequence:
Finish the game using legendary difficulty setting in Campaign Mode
Carry 3 Weapons:
OK to carry 3 weapons u have to beat the game (i beat it on easy) then when ur done u can carry 3 weapons
Using a combination of assault, Shotgun, and grenades works best…
Warning: Only use the [sticky] grenades at a far distance, especially for the little ones.
Shot gun- use on big floods, and little floods.
When those little guys, that jump up at you, are all grouped together use the shot gun, it shoots out a lot of bullets at a time (you can see this if you shoot at a smooth wall, or the ground…you can see all the marks it makes).
Also close to medium range range to the big guys.
Use Assault rifle if the guy is standing still, if he or you are moving too much it screws your aim very badly and you waste bullets and have to re load more often and then they have a clear shot.
For the grenades use them when you know something is behind a wall, or when you see a lot of flood coming at you from a safe distance.
for sticky grenades you MUST ALWAYS REMEMBER to use them at a safe distance because if you shoot it on one of those little guys that follow you you will get hurt bad too because of the blast that they brought with them, same with the big guys; I have learned this because the the Master Chief doesn