All varieties of tea come from the Camellia sinensis plant, but the processing makes a world of difference. Black teas are harvested, dried and well fermented to give them their distinctive flavours. These are the finest black teas you can find.
Keemun is considered by most to be the finest of all Chinese black teas. It's smooth and very aromatic, and can be found in many quality tea blends. Keemun is great by itself, or with a bit of milk and sugar.
Named for the Darjeeling province in India, this fine black tea is another worth trying. The Darjeeling region also produces excellent green and oolong teas. The black teas have a delicate flavour but are still full-bodied.
Another black tea from China, this tea has a strong smoky flavour that many find delicous. It's not for everyone's palate, so you'll have to try some and decide for yourself.
A very full-bodied tea, but without the hint of spice found in Keemun. It's grown in northern regions of India. The flavour is strong and rich, and great with breakfast.
Nilgiri is a lighter and more delicate black tea, from India. This tea is excellent for the novice brewer, as it is a bit more forgiving if not steeped quite right.
If there are too many choices for you to make up your mind, Adagio teas offers a very nice black tea sampler that includes several of the varieties listed above.