Psycannon
Range 24" S7 AP4 Assault 2 Rending or Range 36" S7 AP4 Heavy 4 Rending
Can we say extremly useful weapon. From what I have seen you will be able to take 4 of these in more than just Purgation Squads. This gives you extreme anti-transport firepower that can be on the move. Did we say it has rending? Yes it can take down a land raider. It is an Assault Cannon on steriods. Lets see, 4 guns putting out 16 shots at 36" = Dead Transport. Yes, that is approximately 12 hits. Lets see you make all those coversaves for smoke. The scary part of this is, that would be an average of 2 rends, which means penetrated AV14.
The Psycannon if it holds to be true, looks like it will be an option in almost every shooting unit. So what you get is an extreme shooting army for knocking out transports, and some great assault style troops.
Incinerator
Range Template S6 AP4 Assault 1
Here the Strength of the weapon is the key. S6 doubles the toughness of almost everything that really does need to be hiding in cover, and beats their armour save. Can we say dead Guardsmen, Kabalite Warriors, and just about anything else? No cover save, no armour save, no taking a single wound, just dead. We are approaching flamestorm cannon effectiveness (almost)
Psilencer.
S5 heavy 12. We don't know as much about this weapon this yet, however it looks like it will shred the hordes very effectively. I also don't believe that this weapon comes on much, but it is an option on the DreadKnight.
I see Grey Knights as being a very effective, and not as of yet overly expensive shooting army. The point costs for throwing down a list as such seems to be very reasonable. It is the assault units so far that look expensive. Grey Knights are looking to be a very exciting codex, although we will still have to wait to see if the rumors all hold true.