If you ever want to relive the good old days of Bungie, their Marathon series (the precursor to Halo) are now open source and free to play. You can download them from the link at the top of this comment. There's also an XBox Live Arcade version of Marathon 2 called "Marathon: Durandal". An iOS version is also available.
English
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Dun dun, dun dun, dun dun, duna da, MARATHON!