Luis Fernando Lopez is the protagonist of The Ballad of Gay Tony (2009), the second episode of GTA IV, voiced by Mario D'Leon. He is the bodyguard and business partner of Anthony "Gay Tony" Prince, owner of the Liberty City nightclubs Maisonette 9 and Hercules, and spends the game trying to save Tony from his debts.

Tony Prince's bodyguard, partner and closest ally. Tony borrows from the Ancelotti crime family and from Mori Kibbutz to keep his clubs open, and Luis does the dirty work to pay those debts back, while also helping his drug-dealing friends Armando Torres and Henrique Bardas.
Luis works for Mori Kibbutz, for the Ancelottis through their enforcer Rocco Pelosi, and for Yusuf Amir, a developer who wants to buy Tony's clubs and has Luis steal an attack helicopter, an armoured vehicle and a subway train. A diamond deal Tony sets up is ambushed by Johnny Klebitz's Lost MC. Ray Bulgarin, the diamonds' original owner, turns against Luis and Tony, and Rocco pressures Luis to kill Tony. Luis refuses, defends Maisonette 9, then boards Bulgarin's private jet and kills him, escaping by parachute before the plane explodes. Luis and Tony decide to keep the clubs.

He witnesses the robbery of the Bank of Liberty, Niko's Three Leaf Clover mission, at the start of his story. Later he ambushes the diamond exchange run by Niko and Johnny, and he and Tony recover Gracie Ancelotti, whom Niko had kidnapped, before Bulgarin steals the diamonds.
Niko Bellic, Johnny Klebitz and the full cast are on our GTA 4 characters page.