The listing, HIB 6 - Bonus Games [Steam Key] has ended.
Humble Indie Bundle 6 Bonus games, 1 code activates these for 4 games.
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Jamestown ((Win - Mac)
More info http://store.steampowered.com/app/94200/
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Gratuitous Space Battles (Win - Mac - Linux + Trading Cards)
More info: http://store.steampowered.com/app/41800/
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BIT.TRIP RUNNER (Win - Mac + Trading Cards)
More info: http://store.steampowered.com/app/63710/
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Wizorb (Win - Mac + Trading Cards)
More info: http://store.steampowered.com/app/207420/
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Good luck!