Metal Gear Solid 5's multiplayer's supposed to be revealed this week but cam videos of gameplay have been popping up all over the place since Gamescom. This one's still up for the time being but there are GIFs if it gets yanked.
The mode plays a lot like the main game except you sneak onto another player's customised Mother Base as Snake, avoiding or neutralising guards and security measures along the way. Part of the demo shows Snake 'waiting' on the base until night to take advantage of the darkness. You'll actually be able to steal other people's resources with the video showing guns, equipment, supplies and even soldiers being shipped off using the Fulton Recovery System. If I come back one night and find all my stuff gone I am going to furious.
The demo ends when the other player, who also looks like Snake, shows up. It's not clear if it's actually someone controlling him or a game triggered event.