The most nonlinear game in your opinion?
Actually, the question in the subject.Advise really non-linear game, and not where the pseudo-variance of Aki in the Witcher, and the like.Tetris... seriously.
These games simply do not exist, they are all scripted, and all have a linear plot. All the rest of the wagering. And Tetris only depends on you, where falling blocks. )
It's a game where there are jobs, but there is freedom in the choice of tasks and freedom of their actions in each task. For example is TES 5 Skyrim, where using cheats and mods you can do to build your story and do what I want. Just Cause 2 - freedom of choice and action. Far Cry 4 - a lot of mods with complete freedom. Call of Duty Modern Warfare 2 - special operations - select tasks and complete freedom of action.
Bagels as an option. Is the hero of the first level corridor, and there is a raaz...and from the corner comes the dragon is the sixth level. Generated dungeon, enemies are generated, bonuses are generated, each passage different from the previous one and is not a nonlinearity, when the player chooses the other option, even if it is repugnant to him, and natural, based on the work of the generator. But also play them much more difficult than in any AAA. In fact, the goal is not to go and die closer to the finale:)