I'd be surprised if you haven't seen it already, but Rockstar recently uploaded a video filled with gameplay on their Youtube channel. The video shows footage as a narrator explains some of the gameplay mechanics that will be involved with the game. The three-way main character system was shown and explained, and it looks to be very intuitive.
The video also goes onto showing some of the many things you can do in the world of GTA V, including a whole host of sports like golf, tennis or hunting. And other completely unexpected activities like investing in real estate and buying stocks in a virtual stock market.
Another interesting feature is the ability to completely customize your own car with spray paint, and vehicular upgrades. The video showed the player owning a car that looked to come straight out of some of the older Need for Speed games.
The video is feature packed, and if you've been excited for the game already, this video will probably get you drooling, or at least even more excited for the release this September. The video leaves with a tiny sneak peak of multiplayer, with the narrator hinting at another video coming soon, showing off more about multiplayer in GTA V.
For those that are interested, Rockstar has said that the gameplay footage shown was being played off of a PlayStation 3, although they have said that both games won't have any noticeable visual differences.