What's your favorite gun pack and why?

Customizable Weaponry 2.0, as it's pretty realistic (my friend is mad as he can't use aimbot that well with CW 2.0 :D). There's a ton of customization (well, the name says it, so...), some mods for them (like Weapon Crates or something similar), magazines (when you still got bullets left in your magazine and you drop it, it's gone).