Common Cathode Diodes?

[Axtman]

I am going through some parts and found some common cathode diodes. What is the purpose of these things? Thanks.

[g1]

In the tube world, there were used in radio, with one side being the detector, and the other side for AGC. I would think there are plenty of other applications.

[The Dude]

I see them often used as a full wave rectifier- for whatever reason, more so in SMPS supplies.