Attack Speed

It's not mentioned anywhere in the description nor effects, but for some reason its there in the hint. Its just a Nexon error, right? Its really there?

Yea it's really there. It doesn't give you max attack speed but it does increase it significantly. It does stack with attack speed set effects too. (Note that "Fastest" is not the limit for guns.) I think Set Effect+Frenzy is the limit though. You could also use vivace but all three wouldn't make any noticeable difference if at all. (Though they do effect different things, like delay, which would help if you were to have all three but that's negligible.)