I wanted to run a game where the players can do whatever they imagine, completely free. This kind of game is often called a sandbox, where players can make whatever they want. It has no railroad, no set path that the players must traverse. I have since learned that such a game is long in coming and may actually be unrealistic.
I have had a player whose not so obvious playing style, his goal in every role playing game, was to manipulate and assassinate the other PCs. The difficulty offered by the game was not enough for him. He wanted the power that the game allows, the ability to screw with other people's PCs, other people's art in a real sense. This player is otherwise a good guy. Yet he will never play in my game again. I have been blessed with better players since.
I believe it is the role of the player to come together with the other players, to cooperate using creativity and innovation, facing the challenges and consequences that the game provides. D&D is also a role-playing game, where players create and play unique heroes, an additional challenge compared to a game such as Monopoly. That is all.