My favourite would probably be Cyberpunk because
bias you cannot do any of the stuff you can do in cyberpunk in another texture pack. It was crafted with a theme in mind and it sticks to that theme.
Although I generally use Rupture for medieval, And OrigHD for modernish stuff and futuristic stuff.
To be honest though, I don't think Rupture is very good as a texture pack. It has some good textures, But most of them don't follow a central theme, And a lot of them don't mesh well with each other. The ones which do mesh work near perfectly together, But a good chunk of them are borderline unusable.