* Mission replay system. Can replay any (storyline)mission that were done. Sometimes I miss a mission and there were no savefiles before it, all I can do to replay that mission is to start over the whole game.
* Able to sell cars/car parts throughout the game. Steal a car and sell the parts in black market is a cool way to make money!
* Stealh kill ability like the one in manhunt
* More in-safehouse activities like decorating, write and paste notes on fridge, listen to Music
* I personally love to see Maccer and Umberto Robina again.
* Heads that don't just disappear when popped!
* Wanted level system of GTA4, with collectible bribes also existent.
* Interactions with peds. Can activate a menu with the things you want to do with a ped. Such as: ask directions, compliment on their clothes, random chat, say shit to piss them off...
* Destroyable buildings/environments. You can crash a house by bumping into it. After that it can be seen rebuilt by construction workers.