This tactical support squad is armed with melta guns and the sergeant has in his possession a power fist coupled with a melta bomb. Several of their members are sporting gun kata poses, and all of them have had their height increased through thigh lengthening (i.e. true scale marines). Although true scaling marines really hammers the hobby mojo overall, the final result is worth while. This squad was actually the first to undergo the true scale process, and as such its not the best job I've done. However, the paint scheme with its dents and shiny armour showing through in places hides the worst atrocities of this process, and I've learnt a lot through this squad about the methodology.
As with my Alpha Legion terminators, these marines are very close to completion. Just some attention needed on their weapons and small scale pouches (etc.) and I'll be happy. Its simply a matter of time now!
On the battlefield, I've either played them as the squad that deep strikes through Armillus Dynat's warlord trait, or I have just used a few of them as a special weapons marine inside of a veteran tactical squad. They usually die in my games, but not before they've done some appropriate damage with their melta weapons. And that's fine -- they're worth their points in the damage they can wreck even if they don't survive particularly well.
In case you're wondering, the grey knights back packs are there to signal that they're developed some kind of unique teleporting technologies and that is what Dynat's special rule is suggesting in a narrative sense.