Clues are pointing to Valve adding a new faction to Team Fortress 2, and they may be Robots.
It all started when Valved launched its "most fiendishly difficult" ARG. That led some gamers to notice new bloodstains had appeared on the Team Fortress 2 logo on the main page of Valve's site. They linked to this page, and eventually to this comic.
A little backstory of Team Fortress: The "story" behind the game is that two brothers, Blutarch and Redmond, with the last name "Mann" are fighting over gravel. The new links suggest the existence of a third brother, Gray Mann, may exist to bedevil Blue Mann and Red Mann.
The prevailing theory in gaming is that all of this is pointing to a “Mann Vs. Machine” update. Gray Mann, the theory goes, will bring his robots in and they will function as an entirely new faction in TF 2. We could also see the introduction of new modes, or some other, as yet unforeseen revelations.
Valve may have been dropping these hints in their games as early as two years ago, as evidenced by this YouTube video:
What do you think Valve is up to?