I started writing this some day on another site, so I already got the first 15 episodes. It's written script-style by the way.

I'll start with a character list:

Master Chief:
One of the main heroes. If you know Halo, you know MC (it's the guy you play, duh). He is a good tactician and possesses enormous physical strength. His social life is quite lonely, he rarely talks and prefers to work alone. That's why he hated the fact he had to team up with Arch Devil, who's quite the opposite of MC.

Arch Devil:
MC's partner in war. He might not be as smart as MC, he's certainly stronger and funnier. He's cheerfull, optimistic and reckless. Usually he's the first one to charge towards the enemy, while emitting one shitload of stupid one-liners. He thinks he and MC form a great team, but the MC himself thinks otherwise...

Cpt. Keyes:
The captain and commander of the Pillar of Autumn. His duty to the UNSC is the most important thing he can imagine. Even though he's just an ordinary human, he's certainly the bravest of all. And his humor is a bit, weird.

Cortana:
The AI of the Pillar of Autumn. One of the few who posses a personality. Although she can be bossy some times, the fact she's a brilliant tactician gains her respect among the men. Her ability to hack almost any system makes her really usefull to have around.

Sharagran:
He's a Covenant commander in charge of boarding the Pillar of Autumn. Like Keyes, he also has a strong sense of duty. As an Elite he can leap great distances, and he's physically even stronger then a Spartan.

Brutus:
Meet Sharagran's rival, a not-as-brave-as-the-others Brute. Although he's about as strong as Sharagran, he prefers to let his men do the dirty work. Together with the Prophets and the Chaos Marines, he's devoloping a plan to conquer the universe.

Gravemind:
A hive brain of the flood. In opposition to the normal Flood, he's super-intelligent. He's probably even the most intelligent being in existence.

Admiral Tiberius:
Tiberius is the commander of the Space Marine fleet. Brave, smart and loyal to his master, the Emperor. He's the most powerfull Space Marine around.

Commander May'Sho:
May'Sho is the commander of the Tau fleet. He's rarely seen without his battlesuit. Most of the time he's really calm and emotionless. But on the battlefield he's a force to be reckoned with.

Kais:
He's a Tau Shas'ui (veteran) who aids MC and AD in their quest to destroy Halo. In terms of personality he's also a mixture of the two Spartans. In battle he wields his Rail Rifle with great accuracy.

Chieftain Mortaros:
Chieftain Mortaros is the leader of the Chaos Marines and the main bad guy. He later allies himself with the Covenant (without the Elites) and together they plan for universal domination. He kinda looks like Tiberius but only more demonic.

Well, that's it for now. More characters will show themselves as the story unfolds. The first episode shall be posted soon!

ah, good old Halo DOW

Isn't Dawn of War a WH 40K game?

yes it is, that's why the Tau, the Chaos and the Space Marines are in there

Better to die for the emperor, than live for yourself. I heart the space marines, so I wish you all luck with this fanfic, as both a devoted Halo and Warhammer 40k fan.

Thanks, I really appreciate it.
I shall post the first episode today.

Episode 1: Abandon Ship

Both MC and AD are lying asleep in their cryo-tubes, two crewmen are discussing about them at the command bay.
Crewman 1: Do you really think it would be wise to wake them up? They can be a bit unpredictable...
Crewman 2: We are not here to question the captain, orders are orders, you go down there and get them ready for combat!
Crewman 1: Yes sir...
Crewman 1 walks down to the cryo-tubes.
Crewman 1: Alright sleeping beauties, time to rise from your slumber...
He activates a terminal and the cryo-tubes open, MC and AD stand up.
MC: Orders?
AD yawns and cracks his neck.
AD: What? No bed and breakfast?
Crewman 1: The captain wants you at the bridge ASAP.
Crewman 2 over intercom: We will have you combat ready in no-time, bringing your health, shield and target monitors online now.
AD: Aaah... Much better!
Crewman 2 intercom: Now would you please look at eachother and tell me if your targeting reticule turns green?
Both Spartans look at eachother and rise their thumbs.
Crewman 2 intercom: Good now go to...
Captain Keyes intercom: I want those Spartans at the bridge now!
Crewman 2: But sir! Then we'll have to skip weapons training and...
Captain Keyes intercom: On the double creman!
Crewman 1: All right...
He looks at MC and AD.
Crewman 1: You guys better follow me, let's go.
He runs through the door, MC and AD follow him
Crewman 1: Better keep up!
He runs past a generator, wich explodes killing him.
AD: Blast! Let's go this way!
They run through a long corridor, at the end they see marines and crewmen fighting against Covenant.
Crewman: We're gonna die!
Marine sergeant: Shut up and fight!
The blast doors between the marines and the Covenant close.
Marine sergeant: The captain is waiting, follow me to the bridge.
They follow the sergeant through more corridors with even more marines and Covenant fighting. Finally they arrive at the bridge, they walk towards the captain while the sergeant returns to the battle.
MC: Captain Keyes...
AD: Sir!
He salutes.
Captain Keyes: At ease Spartan, as you should probably know, the Covenant are boarding the Autumn. Capture of the ship's A.I. is unacceptable, so it's your mission right now to get it of the ship.
Cortana appears.
Cortana: Hey guys! Mind if I take along?
AD: Oh no...
Captain Keyes: Get her off as quickly as possible. Now go!
MC plugs Cortana in his helmet.
Cortana: Alright, plugged in and ready to go!
MC: You just be quiet, we will do the shooting.
AD: Sir, in case you didn't notice, we could use some weapons.
Captain Keyes: Here, take this, it's the keycard to the armory.
He hands over the keycard.
AD: Thank you sir.
Cortana: Sir, a new wave of boarding craft are heading towards the Autumn!
Captain Keyes: That really means it's time for you three to go!
MC + AD: Sir yes sir!
They both leave the bridge.

End of part 1...

I like the way how you make it look like a movie script

And you stole my last name

Sorry! I won't do it again!

I don't blame you. Didden is an awesome surname

Yeah, we Diddens rock.

Believe me, it doesn't get any better than Wackers. ([a] like in [are])

Diddles. Taste the rainbow. xD

it took some time, but here's episode 2!

Halo DoW part 2: Invaders

E'Shar Granumee, known amongst his troops as Sharagran, and his squad of Elites are waiting inside one of the boarding craft heading for the Pillar of Autumn. he stood up, so everybody could see him.
Sharagran: Hear this, my mighty warriors, the humans think they can just set foot on our Halo! We will not let that happen! We shall stop them from touching Halo's sacred grounds! In a few moments we will hit their puny ship. Some will die, but none shall die in vain! The Great Journey is at hand!
The Elites activate their plasma swords and roar, while Brutus calls Sharagran over his radio.
Brutus (radio): Not afraid my friend?
Sharagran: Shut up... and don't call me friend!
Brutus (radio): Easy, remember your mission! Open the cargo doors so our dropships can enter ...friend.
Sharagran: Don't worry, I'll finish your mission ...coward.
Brutus (radio): Brutus out.
An Elite with red armor approaches Sharagran.
Red Elite: Just leave him, he doesn't know any better.
Sharagran: Now that's just it, I think he knows a lot of things that haven't been told to me...
At that moment the craft hits the Autumn. Sharagran puts on his helmet.
Sharagran: This is what we've been waiting for! Go forth! And fear neither death nor pain!
Sharagran and the Elites charge in, they catched the marines by surprise, and could quickly dispatch them.
Blue Elite: They didn't stand a chance!
Red Elite: Stay on your guard...
They approach a closed door.
Sharagran: Engineer, destroy this door.
A blue Elite plants a satchel charge on the door, they all take cover and the door gets blown away.
Sharagran: Charge!!!
The Elites charge in and start hacking and shooting at the marines, this is also a quickly-won battle. The Red Elite spots a crewman trying to run away.
Red Elite: Over there! The coward is trying to run!
Sharagran: Capture him!
An Elite jumps on top of the crewman.
Sharagran: Good job, warrior.
Elite: Thanks, commander.
Crewman: Please! Don't kill me!
Sharagran picks him up at his collar.
Sharagran: We won't, if you tell us where we can open the cargo doors.
Crewman: The gate controls, get to the gate controls! Follow corridor C- 24, just don't kill me!
He points at a large door.
Sharagran: Thank you for your help.
Sharagran, the Red Elite and most of the other Elites open and enter the door. One last Elite roars at the confused crewman, which runs away screaming. At the end of the corridor a marine walks out of the gate control room.
Marine: Holy shit!
He tries to shoot at them, but gets stabbed through his chest by Sharagran's plasma sword. The Elites enter the gate control room.
Sharagran: Now how do we open this?
The Elites look at eachother for a moment and raise their shoulders.
Sharagran: Well then, there is always one thing I can think off...
He smashes the console with his fist, somehow, the cargo doors open.
Red Elite: Well would you look at that. It worked!
Multiple Covenant dropships land inside, Brutes hop out and kill the marines which are trying to retreat.
Sharagran: Reinforcements are here, move out!
A cargo elevator to the left of them takes them down to the cargo bay, Sharagran approaches a Brute captain.
Sharagran: Is Brutus with you?
Brute captain: He had to leave, he was summoned by the prophets for a meeting.
Sharagran: Great...
Brute captain: But he ordered us to secure the bridge and capture their commander.
Sharagran: And of course he let's us do his dirty work...
All the Brutes regroup behind the captain.
Brute captain: Advance!
The Brutes follow the captain towards the cargo elevator.
Sharagran: Let's join their party, shall we?
The Elites roar and they all hop on the cargo elevator.

End of part 2...

And of course I already read this one, but it stays awesome