The Master of the Adeptus Administratum
Lord Commander Militant of the Imperial Guard
The new Marine codex introduces a whole new weapon type to the game of Warhammer 40,000.
There’s new article up on Faeit 212 posted by Nafka:
Grav-Weaponry and Its Dramatic Effect on Our Game
http://natfka.blogspot.ca/2013/09/grav-weaponry-and-its-dramatic-effect.html#more
There are a few parts to the rules for these weapons which look like they need a bit of FAQ help, but one thing is for certain: They’re here to stay.
Astronomi-con 
I take exception to grav weapons on a few levels. First, fluff and background. Grav weapons were supposed to be extremely rare. Any old marine can take one now. Second, the rules need some clarification. For example, Dark Eldar Archon with Shadowfield. Is he wounded on a 5+(his armor save) or 2+? While it makes sense to apply the 5+, I am certain it will cause arguments. Also, as was pointed out on the link, there is some discrepancy as to what happens if you hit a vehicle multiple times. Again, I agree with his views but it leaves some wiggle room. All in all, while the book looks beautiful and some of the new stuff is great, it feels quickly thrown together.