Warhammer 40,000 – Shock troops are only good when you can get them across the board protected. When they don't have the option to deep strike they need a transport. The humble rhino is the cheapest way to get them there.
In this edition the Havoc Launchers are a must take item for any Chaos Marine rhino, D6 strength 5 shots can ruin anyones day. Combined with combi-bolter (or other combi weapon of your choice) and you have a decent shooting threat in addition to the cargo it needs to move across the board.