HALO

HALO>SINGLE PLAYER>LEVEL WALKTHROUGH>HALO

Ideal arsenal: sniper rifle and alien rifle
Best tip: Park your Warthog within 50 meters of life pods. If you keep it manned with soldiers, these guys will wipe out tons of aliens for you.
Hardest part: when you need to rescue your buddies from an alien base, you will be attacked from above and below by alien forces.
How to beat it: park your Warthog (with soldiers in the gunner positions) so that it provides cover fire for you. Then quickly make a run to get inside the base. You'll pick up extra troops who'll help you wipe out the rest of the aliens.
Cool thing to try: the Warthog is an excellent offensive weapon. Use it as a battering ram. Watch out for plasma grenades; they're deadly.

WALKTHROUGH

    Out run the Banshees by hanging close to the far left side of the map. If you want to shoot thm down, do it. When you reach the first base, the aliens will send drop ships. These typically land on alternating sides of the base, but keep an eye on the skies. One trick is to drop a grenade just outside thr drop ship when the Covenant forces are exiting.
    When you get the Warthog, make sure to keep gunner alive. He's you biggest support. When you enter the bridge room, get the most out of your gunner; let him pick off the aliens at a distance. Then park nd let him cover you as you head to the right-side hand of the building to turn on the bridge. The switch is through a small passage on the right side.
    First find a life pod crash site and get yourself the sniper rifle. Then, you'll see a path on each side. Go left first. Park your Warthog and gunner in the open area overlokin the base. Use yourself as bait to draw alien attention if needed. Rescue your troops, and if possible, pick up a soldier on the passenger seat of the Warthog. Do the same at the other base. Try to get into the base as quickly as possible and find your buddies. Once you've killed all the aliens in your area, head up to the next area. Find the crashed excape pod and park your Warthog nearby. Grab the sniper rifle by the pod. Head up to high ground and use it to pick off Covenant while your Warthog gunner takes care of the rest.
    Once this area is cleared, head to the next area and follow a similar strategy. Park your Warthog by the lifeboat, then head to high graound and snipe. Jump on the drop ship and split.