Plasma Storm Battery (Dark SpeederVengeance): Is it me or this looks like a twin-liked version of the Plasma cannon found in the Leman Russ Executioner? that would be a 36" S7 AP2 Heavy 3, twin-linked! pretty devastating but sadly a AV10 platform with 2 hull points isn't exactly durable. I wonder what Mr. Vetock is keeping up his sleeve?
Rift Cannon (Dark Talon): This is the strangest of the lot. Rumours mention that the rift cannon being related to warp technology somehow ("cracks a hole in reality and creates an implosion"). The look of the weapon is also that of a gun with a strong recoil and low rate of fire, so this is looking to be a blast, medium/large strength sort of gun. Perhaps with some fancy special rule (i.e. ignores cover or the like). My bet is S6-7 AP4 Large Blast Ordenance 1
Stasis bomb (Dark Talon): Very little is known of this, just that is featured in the Dark Talon and that is one-time only. There's a hint in which the Dark Talon is good at both suppressing and weakening the enemy infantry, so this is where the bomb could come to play - causes some sort of adverse effects but no wounds. I just hope it's not like psychotroke grenades - keep the cheese away from DA please :)
Avenger Mega Bolter (Nephilim jetfighter): It has the looks of the Vulcan Mega Bolter (60" S6 AP3 Heavy 15) but the name is different and it seems a gun too large to be fielded in a light flyer; this a weapon is only found in some Titans and super heavy tanks after all. On the other end we have the Gatling psilencer that has a 24" S4 AP- Heavy 12 profile. Combined with the Heavy bolters this yields 15 S4/5 shots but its not very impressive in an army full of bolters of all flavours and plasma. I would also dismiss the gatling gun (S5 AP- Heavy 15) found in the Leman Russ Punisher as it is not a proper bolter gun (it belongs to the autocannon family).
Where do we end? the WD copy mentions the Nephilim being good at taking out enemy flyers (so AV10-12) and light mech, so I expect it to fall in a reasonable middle term between the OP Vulcan bolter and the meh Gatling psilencer. Some S6-7 with a high rate of fire.
Something else to note is that the heavy bolters sponsons have only been spotted next to the Avenger Bolter but not with the Rift Cannon or TL las cannon. Perhaps an indication that the Avenger Bolter is a less powerful weapon than the others?
Blacksword missiles (Nephilim Jetfigher): Probably a sort of Hunter Killer missiles (S8 AP3 heavy 1 shot) or a small variation (like BA's Bloodstrike missiles found in their Storm Raven) that have AP1 instead. A completely different profile is not to be dismissed if we look at the missiles featured in the GK version of the Storm Raven, that are especifically anti-psyker. In any case a 1 shot missile and a different profile to the Skyhammer found in the Storm Talon (60" S7 Ap4 Heavy 3) if the illustration below is representative.
Plasma Talon (Ravenwing Knights): While this has the look of a twin-linked plasma gun, I suspect the name has been changed to accomodate different stats. Specifically a lower range as the bikes are very mobile themselves. So perhaps a 6" version of the plasma gun we all know (and that some also love).
Grenade Launcher (Ravenwing Knights): This again has the look of a known weapon (astartes grenade launcher) but rumour has it could be related to the stasis bomb, perhaps reducing the enemy to I1 so the hammers strike at the same time. Speaking of which, I don't think a unit that already sports TL plasma and thunder hammers really needs more toys.
Corvus Thunder Hammer (Ravenwing Knights): I dont expect it to be more than fancy Thunder-Hammer, not even master-crafted. A few thunder hammers in a highly mobile, T5/3+ platform is nothing to sneeze at, especially when you consider all those plasma shots before the assault!
Mace of Absolution (Deathwing Knights): Perhaps a master-crafted variant of the standard power mauls with the rumoured 1-time Smite ability.
Flail of the Unforgiven (Deathwing Knights Grand Master): This could honestly be anything, but I'd be surprised it's not AP3 or lower or will seriously suck at challenges. It would also make for a strange unit with 5 storm shields and not a single AP3/AP2 weapon. The shape of the weapon with multiple parts could suggest a re-roll to hit? (it already strikes at S6)
Massive Halberd of Caliban (Deathwing Champion): hmm power axes are already AP2 and have a Strenght boost. This is a 2 handed weapon so it needs to gain something over losing the ability to carry a shield or a gun. More strenght would just make it a bog standard power fist so... do you see where I'm getting? yes looks like there will be some fancy rule here. Astorath's Executioner Axe is a 2-handed axe and its special rule is making your opponent reroll passed invulnerable saves.
Anyway we'll only have to wait a few more days to find out. What are everyone's bets / guesses?