Luis Fernando Lopez
Luis Fernando Lopez is a Dominican-American street gangster associated with the Northwood Dominican Drug Dealers and also works as a bodyguard for club owner and Ancelotti associate Anthony "Gay Tony" Prince. He is also be rumored to be involved in underground fight clubs. Luis appears during Grand Theft Auto IV on three occasions. The first time he visits the Bank of Liberty branch in Algonquin during the bank robbery pulled off by the McReary brothers and Niko Bellic in the mission Three Leaf Clover. Fellow hostage Eugene Reaper suggested that they stand up to the robbers. Luis stated it was a bad idea, which was proven when Eugene killed Keane and was then shot dead by Packie and Derrick. Luis escaped unharmed when the surviving robbers fled the scene. The second time, he ambushes the diamond deal that Niko was making with Isaac Roth on behalf of the Pegorinos in the mission Museum Piece. It has also been speculated that Luis worked with Johnny, but he was there with the Ancelotti Family when the deal crashed, and he shot at Johnny. The third time he went to the diamond/Gracie Ancelotti exchange with Gay Tony in the mission Diamonds Are a Girl's Best Friend.
There is some speculation he will be the protagonist in the second episode of the DLC. Reasons to support this are his mysterious appearances in Grand Theft Auto IV, and questionable background. This is also suspected due to Niko and Johnny, two protagonists, meet up in the museum, and Luis appears to ambush it. As well as the achievement you get after completing the Museum Piece mission is called "Impossible Trinity", which at first is crpytic, but makes speculative sense: 3 characters have been brought together by almost impossble events. Whether or not he appears in the second episode of DLC is still up in the air, but by his mysterious appearances, he may be featured more in The Lost and Damned.