Victor Coste

Serving as the narrator and main help to Sam Fisher in Splinter Cell: Conviction, Coste was a huge help in Sam's revenge.  Coste served under Fisher in his Navy SEALs squad, even going so far in Iraq to disobey orders and saving Sam's life at the hand of the enemy.  He was a close friend, and an even better ally going into Conviction.
 
Post his life in the military, he opened his own private military company. During the events of Conviction, he would use his ties from his job in order to supply Sam with the best equipment money could buy.  He would even help Sam out by helping save Sarah Fisher, and getting Sam close to the White House.
 

At the end of Conviction Coste was under the arrest of the Black Arrow private military company.  He is shown narrating the events of Conviction, and his final words are about how Sam said he was like a brother to him, and how he never leaves family behind.  Shortly after, sirens and alerts are heard, giving the assumption that Sam is coming to save Coste, for no family member will be forgotten.