PC players can download the excellent Assassin's Creed: Black Flag for free next week, as part of Ubisoft's Happy Playdays seasonal promotion.
If you fancy downloading the rip-roaring, piratical high seas adventure (which I still reckon is the best Assassin's Creed game, but then I'm easily swayed a peg leg and a palm tree), it'll be available between Monday December 11th and Monday December 18th.
If you're after a more immediate freebie, however, Ubisoft is also giving away a PC copy of alternate-history RTS World in Conflict, plus its single-player Soviet Assault expansion, right now. You've got until December 11th to grab it.
