Amazing Quest Idea

Some old and even new rpg is quite linear. They have line event system. Everything goes step by step and looks like this:

 Some awesome ( Witcher, TES, Gothic ) new RPG have tree like quests. Thats can be different trees but anyway:

Of course some gamedev guys are cheating and do something like:


And no one have quite simple but the most interesting way of quest system that was quite obvious:

Of course it is much complicated, because amount of connections. But as result much more ways to complete the game.