Caestus Assault Ram
The Caestus Assault Ram is a Space Marine vehicle originally developed for boarding other spacecraft. Its magna-melta fires a shot to weaken the enemy's hull, and then the armored prow smashes its way in. Meanwhile, the occupants are held in a restraint system that protects them from the shock of entry; the restraints are so big that they can accommodate Terminators as well as regular Space Marines, so the Caestus can deliver a full squad of any kind of Marine imaginable. Once the Assault Ram has penetrated the enemy hull, the assault charges disrupt any defenders with shrapnel, the clamps release, the hatches drop, and the occupants join the fray.
Eventually, the Space Marines realized that the traits that made the Caestus so good at assaulting spacecraft made it very well-suited for ground attack as well. The magna-melta doesn't care whether its melting a hull, a bunker, or a tank, and the restraint system and durable internal structure and hull meant that the Caestus could make steep orbital drops into zones too dangerous for a Thunderhawk or Drop Pod, especially once it had been upgraded with anti-gravity panels like the Land Speeder. So now some Space Marine chapters make ground assaults using Metal Boxes falling from the sky like Steel Rain.
The Caestus Assault Ram's model was created by Forge World for their Imperial Armour volumes covering the Badab War.