I can invest my money into stocks in the game? That's awesome. Also the Golf 'mini-game' looked surprisingly real/authentic. I love golf so the fact that they showed you can do it in game particularly caught my eye. I wonder just how these little types of things will play.
This will most likely be the one game I buy this year (last year it was only Halo 4). GTA always brings it, and this gameplay trailer (which is how all trailers should be done btw) proves that.