Razorback Transport
The Razorback was developed after the Horus Heresy, and was intended to provide Space Marines with heavier fire-support. By replacing some of the Rhino Transport's crew and cargo capacity with ammunition storage and weapon hardpoints, the new transport vehicle becomes capable of bringing troops into the battle, and providing amicable close-support once there. The notably-reduced crew capacity means that the Razorback can only transport smaller squads into battle, but the heavy weapons it adds to the mix makes for a very cost-effective way to get stronger guns on the table for cheap, whilst still providing transport The Chaos Space Marines were intrigued by the design after encountering it, but ultimately decided to simply arm their Rhinos with support weapons instead. as such, it remains unique to the Space Marines.
Overview
It's no tougher than a Rhino, with identical armor on every side. It holds fewer passengers as well. More to be added when this guy isn't hung over.