The Actors of Warhammer 40,000

Dawn of War (The original series)

Paul Dobson - Captain Gabriel Angelos, General Sturnn, and the original voice of Eliphas the Inheritor.
Scott McNeil - Lord Bale, Sindri Myr, Lord Firaeveus Carron (MEHTAWL BAWKSES!!!), Captain Indrick Boreale (SPESS MEHREENS! FOR THE EMPRAH!), The vast majority of the Imperial Guard faction, Chaos Daemon Prince, Chaplain Varnus, and the original voice of Captain Davian Thule.
Brian Dobson - Pretty much the entire game. Mostly plays as the Orks and Space Marines.
Michael Dobson - Colonel Carus Brom and Inquisitor Mordecai Toth.
Steve Blum - As the Vindicare Assassin.
Mark Oliver - As Librarian Isador Akios.
Nicole Oliver - Farseer Macha, Farseer Taldeer and Farseer Caerys and Howling Banshees.
Lee Tockar - Shas'O'Kais

Paul Dobson - Captain Gabriel Angelos, most of the Kheyos Spehss Mehreens.
Brian Dobson - Most of the Ork and Spehss Mehreen units, and the default Space Marine Force Commander.
Scott Mcneil - Neroth the Chaos Sorcerer and Sergeant Major Merrick.
Steve Blum - Lord Eliphas the Inheritor, Spike "Cyrus" Spiegal, Martellus the Techmarine, and the Retribution Chaos Space Marines in cutscenes.
Philip Anthony Rodriguez - Thaddeus, most of the male Eldar units and the adviser.
Keith Ferguson - Ronahn, Apothecary Galan, Plague Marines, the LORD Commissar, Ork Nobs, the grot adviser, the Mekboys, and Chaos Heretics.
Richard Doyle - Lord General Castor.
Patrick Seitz - Failbaddon the Despoiler and Kaptin Bluddflag.
Ian Gregory - Tarkus and Apothecary Gordian.
James Horan - Avitus, Chaos Dreadnought, and the Warp Spider units.
Fred Tatasciore - Araghast the Pillager, Present day Captain Thule, Ulkair the Great Unclean One, Khornate Bloodletters, and Veldoran the Warlock.
Alain Shearman - Jonah Orion and the Ork Wierdboyz.
Christine Dunford - Eldar Banshees and the Farseer.
Christine Potter - Inquisitor Adrastia
Keith Sazabjka - Apollo Diomedes, the creepy Chaos adviser, and Eldar Wraithguards.
Tom Kane - Chaos Plague Champion hero.
Megan Hollingson - Autach Kayleth.
Zach Hanks - Catachan Devils,
Gideon Emery - Imperial Guard Sentinel.
Lani Minella - The now scarier voice of the Hive Mind.

Tom Baker - The voice of the Narrator (Which he did a pretty good job at). Better known as the Fourth Doctor from Doctor Who. Would you like a jellybaby?
BRIAN BLESSED!!! - The Voice of Admiral Constantine. Many a Warhammer fan rejoiced to hear the deep, booming and sexy voice of Brian Blessed in the game (GORDON'S ALIVE!?!).
Sean Pertwee - The Voice of Governor Severus. Fire Warrior is noted to be Pertwee's first role as a character of a Warhammer 40,000 game (He is rumored to voice a character in a possible Space Marine sequel).
Peter Serafinowicz - Who you may (not) remember as the voice of Darth Maul for his single line, voices Captain Ardias.
Burt Kwouk - The Pink Panther actor, well known for his performance as Cato, as the voice of El'Lusha.
Gary Martin - Space Marines.

Trivia: This is apparently the only Warhammer game to feature a main cast of well known actors.

Mark Strong - Captain Titus. The actor is also well known for his performances in Kickass, Stardust, Green Lantern, Sherlock Holmes and Robin Hood. The game is noted to be one of the rare times Strong has played a hero (Since almost all his films portray him as a villain).
Richard Hawley - Sidonus
Noah Huntley - Leandros
Danny Webb - British actor and voice actor for some Warhammer 40,000 audiobooks as Inquisitor Drogan.
Mark Lewis Jones - Welsh actor, who you may remember as the Trojan Captain from Troy, as Nemeroth.
Christine Roberts - Lieutenant Miranda "Mira" Nero
Neil Maskell - Warboss Grimskull

Terence Stamp - (KNEEL BEFORE ZOD!!!) as Captain Severus (And yes, a different Severus) and the Daemon Prince.
John Hurt - As Chaplain Carnak. You know, it's a pity he had less screen time.
Sean Pertwee - As Brother Proteus. Pertwee's second time as a Warhammer character.
Steve Waddington - Who you may remember from his small role in Sleepy Hollow as Brother Verenor.
Johnny Harris - As Brother Nidon.
Gary Martin - Brother Hypax.