Rare. Rare allows the perfect balance, where the juices flow freely without being too gelatin or too cold. I don't enjoy medium, and can't eat medium well and above. Absolute waste of a steak.
Also, to everyone who burns the stuff out of their steak for the fear of blood, there is no blood in a steak. Only a tiny amount of blood is left in the tissue of red meat when it is sold in a store, and it is lost when cooked. The red juice in the meat is a mixture of water and protein called Myoglobin, it tastes good, adds flavor and juiciness to the steak, and is not bad for you at all. I can't imagine a reason why anyone would have to be scared of it.