Rain

One of my personal favorites in the Mortal Kombat universe is Rain. Rain has water powers to which he uses quite effectively to his strength and ability. He made his first appearance in the Nintendo DS game, Ultimate Mortal Kombat but was not a playable character until Mortal Kombat: Trilogy. He resides in Outworld meaning he is allied with Shao Kahn. Rain is only a DLC character in Mortal Kombat 9 meaning he is not a part of the main story of number 9.

His Fatality moves in Mortal Kombat 9 are: 

Bubble Burst: Back, Forward, Down, Back, Block

Does it sting: Up, Down, Back, Forward, Triangle/Y

Reptile

Another one of the most well known and oldest of the Mortal Kombat characters is Reptile. Reptile was in the very first Mortal Kombat game, he was a secret unlockable boss fight in the first game and became a playable character in the second game. He is the one of the few characters of Mortal Kombat to appear in all of the games. Reptile's species Saurians originates from the world of Zaterra. Reptile is the only one of his kind left in the Mortal Kombat universe because of Shao Kahn destroying his home world.
The controls for Reptile's fatality in the latest game, Mortal Kombat 9,are:

Acid Yak: Forward, Forward, Down, Up, X/ A
Weight loss: Down, Down, Forward, Back, Square/ X

Baraka

The next character of which I have chosen to discuss is Baraka!
Baraka is one of the oldest of the Mortal Kombat participants, appearing in the second
game of the series. He originates from Outworld which is an evil realm under the control
of Shao Kahn. Baraka uses two razor sharp blades in his arms that he uses to cut through
his enemies. His fatality moves are:

Up The Middle: Back, Forward, Down, Forward, Front kick/Square or X (Sweep)
Take A Spin: Forward, Forward, Down, Down, Front punch/ X or A (Sweep)