Dark Angels
The Dark Angels were the first Space Marine Legion to be formed by the Emprah. Their Primarch was Lion El'Jonson. As a result, the Dark Angels are totally gay, their Primarch happening to apparently be named after a homosexual poet.
The original Dark Angels had black armour, back in the days of the Corvus pattern helmets. Modern Dark Angels instead use a dark green colour, except for the Deathwing company, which is composed entirely of bone-white Terminators. They were introduced in the Deathwing expansion to 1st edition Space Hulk with a spiffy background story by Bill King.
They also have the Ravenwing, an entirely Bike and Landspeeder company whose Master possesses one of the last jetbikes in the Imperium. As if that wasn't enough, it has a fuckass huge PLASMA CANNON bolted on.