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Halo: Combat Evolved (2001)
More than just introducing Master Chief — inarguably gaming's most iconic space marine — Halo: Combat Evolved made Microsoft's fledgling Xbox a real contender in the console wars. Its spot-on controls and sprawling sci-fi story also proved you needn't be a PC snob, exterminating extraterrestrials from behind a mouse and keyboard, to enjoy a genre-defining first-person shooter experience.
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Halo 2 (2004)
Following the Halo-obliterating events of the first game, this sequel put players back in Chief's Spartan battle boots, but also let them tear things up as disgraced Covenant Elite Commander, Arbiter. This decision — as well as the campaign's abrupt cliffhanger — divided fans, but the new ability to dual-wield death-dealers and play online with friends overshadowed Halo 2's shortcomings.
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Dead or Alive 4 (2005)
The award for most un-Halo game to incorporate a Halo call-out doesn't go to Guitar Hero III — which supported a download of the sci-fi epic's stirring theme — but Dead or Alive 4. That's right, the fighting franchise known for its high-kicking hotties added Spartan-458 or, simply, ''Nicole'', to its fourth entry's roster. Surprisingly, DoA's developers resisted the urge to craft a cleavage-sporting space marine in favor of a fighter that looked pretty much like Master Chief.
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Halo 3 (2007)
John-117's Xbox 360 debut saw the franchise following an if-it-aint-broke-don't-fix-it formula, complementing familiar Covenant-crushing gameplay with sharper visuals and some special effects-spitting set pieces capable of making Michael Bay blush. New support gear, like the super-slick bubble shield, added subtle variety, but it was the Forge multi-player map editor that truly separated this trilogy-capper from its predecessors.
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Halo Wars (2009)
Set 21 years before the events of Halo: Combat Evolved, this real-time strategy spin-off successfully made the cerebral genre's notoriously tricky controls work on a console while also proving miniature Warthogs could be just as cool as their big brothers. Despite solid mechaincs and a faithful adaptation of the universe though, this strategy-focused, Master Chief-less entry failed to register with mainstream fans.
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Halo 3: ODST (2009)
Subtitled for its Orbital Drop Shock Troopers, this experimental side story trades Master Chief for the titular ''Helljumpers'' and tells a darker story from the perspective of different characters through flashback missions. Coupled with the world's exploration-encouraging openness, this narrative device offered something fresh, but it was the addictive live-as-long-as-you-can Firefight online mode that kept trigger fingers engaged long after the credits rolled.
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Halo: Reach (2010)
Another Where's-the-Chief entry, this Combat Evolved prequel again benches the Spartan badass in favor of a new character. Despite the series' star's absence and lack of any significant gameplay innovations though, Reach polishes everything from the previous entries' solo and online experiences to a blinding sheen, delivering what many — including this faithful fan — believe is the best Halo to date.
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Halo: Combat Evolved Anniversary (2011)
This decade-celebrating remake of the title that started it all does much more than just give Master Chief's debut a pretty new HD paint-job; on top of supporting Xbox 360 Achievements and allowing a pair of Covenant-battling buddies to tackle the campaign online, it revisits fan-favorite multi-player maps from Halo 2 and even encourages the most seasoned Spartans to seek out story-expanding Easter eggs.
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Halo 4 (2012)
After five long years, patient fans are not only seeing the start of a brand new Halo trilogy but also the return of their beloved Master Chief. Perhaps more significant — not to mention scary — however, is that this next numbered sequel is the first not to be handled by Halo creators, Bungie Studios (currently working not-so-secretly with Activision). If early reviews are to be believed though, Chief's new caretakers at 343 Studios seem capable of starting the fight all over again.