Shunned by many legions, but embraced wholly by others (Death Guard in particular, but also the Alpha Legion, etc.), the Destroyer Squads make use of dread weapons from the pre-unification Terran wars: rad grenades, missiles, phospex bombs, bio-alchem munitions and so forth.
The rad grenade weaponry is interesting: it lowers the toughness of the opposition on the first round of melee, making for an easier kill. Thus, although destroyer squads are competing for an elites slot against terminators, veteran tactical squads, apothecaries (and everyone else), they're actually a rather interesting option! This is doubly so against other legion armies, even if they haven't got a suite of AP3 or better weapons to utilise. And the models produced by Forge World look cool as well(!)
Here are a few builds that entertained me.
10 Destroyer space marines, 2 rad missile launchers with suspensor webs, rhino with havoc launcher (350 points).
This build is one that lays down suppressing fire with the rad missiles (and hopefully takes out infantry along the way) whilst using the rhino to speed it in to close combat range. The havoc launcher on the rhino simply adds extra suppression fire in the hopes of forcing a rout / morale check to back field units.
5 Destroyer space marines, jump packs, melta bombs, 1 hand flamer, sergeant with power weapon (275 points)
A jump infantry squad to threaten vehicles and counter any incoming squads wanting to kill them. The optimal way to take these guys down are with incoming fire power. Hence as long as they're on the move and sensibly using cover, these guys can really lay down a lot of pressure to the widest variety of enemy units possible.
5 Destroyer space marines, 1 rad missile launcher, sergeant with power fist (190 points)
A cheap, all round, multi purpose squad. Use to sit on objectives / deny objectives, engage enemy infantry and power fist / krak grenade some light transport vehicles on the odd occasion. Add a rhino for extra flexibility.