Rockstar recently posted a picture of a creature that looks like Bigfoot on their newswire.
Some people suggest that they have seen Bigfoot in GTA San Andreas, however most people are agreed that it’s nothing more than a false rumour. This time there seems to be proof that Bigfoot will actually appear. Not in GTA though, but in Undead Nightmare, the second DLC pack for Red Dead Redemption.
More info about the Bigfoot rumour