Sub Zero

The most iconic character in the MK series for me personally is Sub Zero. He was the very first character I played in the Mortal Kombat games and is another personal favorite of a mate of mine. The original Sub Zero is now known as Noob Saibot. The Subzero played in the games after the first is Kuai Liang. He is an assassin for the Lin Kuei. He is the arch nemesis of Scorpion who blames him for the death of his entire clan and family. His alliance is to the good people of Earth realm who are against Shao Kahn. He uses Ice as his power to fight in the Mortal Kombat tournament and just a side note, when ever my mate plays Scorpion and Sub Zero, we refer to it as a Match of Ice and Fire.
His fatalities are:
Have an Ice day: Back, Forward, Down, Forward, Circle/B
Spinal Smash: Back, Down, Back Forward, Triangle/ Y 
Spine Rip: Forward, Down, Forward, Triangle/ Y (this is only with the pre-order DLC)

Scorpion

Scorpion is arguably the most well known and iconic Mortal Kombat character in the entire series. He has appeared in every single game in the series and has been a playable character in all as well. What drives Scorpion to fight is his determination to avenge his clan who was slayed by Sub Zero. He is not inherently evil, however he joins the likes of Shao Kahn who promise the resurrection of his family and achieve vengeance on Sub Zero. An attack in which he has used in every game is his spear attack (which can be seen in the Mortal Kombat-Bush Gif to the left), is always accompanied by the taunt 'Get over here' or 'Come here.' 
His fatalities are:

Split Decision: Forward, Down, Forward, Y/Triangle
Neither Gate: Back, Forward, Back, A/X
Toasty: Down, Up, Up, Y/ Triangle (this requires the DLC of Scorpion's classic costume)

Johnny Cage

Another request by a mate of mine. Johnny Cage is another very old character in the Mortal Kombat universe, making his first appearance in Mortal Kombat 1. His alliance is to Earthrealm and is against the evil forces of Shao Kahn. He entered the tournament to prove his 'kombat' skills to movie critics who believed he was nothing but an "actor who relied too much on stunts and camera work." Whilst he is arrogant at times, he has always been an effective fighter for Earthrealm. He is another of my favorites to play.
His fatalities are:
Heads up: Forward, Forward, Back, Down, O/Y 
And the winner is...:Down, Forward, Down, Forward, X/A

Noob Saibot

The next character has been a request from a user. Noob Saibot is another one of the older characters in the Mortal Kombat series making his first appearance in number two. However Noob has a fairly complex story of his "creation!" Originally he was Sub Zero, one of the most powerful (and well known in the Mortal Kombat universe) assassins in the Lin Kuei. After the death of Sub Zero at the hands of Scorpion (another of the most well known MK characters), his soul is corrupted for many years until he is resurrected as Noob Saibot. His only goal in all the Mortal Kombat games is to rule the Netherrealm and serves no one but himself.
His fatalities are:
Make a wish: Back, Forward, Back, Down, X/A
As One: Down, Down, Back, Down, Block

 

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)