Kali

          Kali is the Hindu goddess of time, and, with that, death.  She is supposed to be a form of the goddess Parvati/Shakti.  Kali is worshiped because she can free humans' souls, destroy ignorance, and help those who want to learn gain knowledge.  Some Hindus believe that before Kali came into being, humans lived forever.  There is a myth where Kali was able to kill an evil demon who was wreaking havoc in the world.  The other gods were afraid to kill it, because every drop of blood that it spilled instantly turned into another demon.  Kali spread her tongue on the ground so that the demon's blood would not reach it, and then killed him.  After that, she became drunk on the demon blood and romped around killing everyone in her path.  She only stopped when her husband, Shiva threw himself at her feet.  She came to her senses then, and became Parvati again.  Today, Kali is one of the very few gods/goddesses where sacrifices of blood are given. 
As you can see in the picture, Kali is holding the demon's head in one of her hands, and Shiva has thrown himself at her feet.  She is also wearing a necklace of skulls.

Source:  http://www.thebuddhagarden.com/kali.htm