3. The Master Chief
There are almost as many references to video games in Grand Theft Auto V as there are movie and internet culture nods, with a distinctly self-referential flavour in Rockstar's inclusion of Easter Eggs from Max Payne, Manhunt and the as-yet-unannounced Agent (as well, of course, as references from other GTA titles.) And among the other Rockstar nods there are some - such as the Claptrap appearance previously - from other mega-selling game franchises, proving that the developers aren't completely averse to showing their respects (though clearly the NPCs criticising the "city of saints" is less charitable.) Continuing that respect, there's an NPC hanging around the Cinema Doppler (a smart reference to it being a copycat of the Chinese Theatre) dressed quite obviously as Halo's Master Chief... The Master Chief also makes a second appearance - albeit in miniature form - in the game...
How To Find Him Head to the Chinese Theatre-twin the Cinema Doppler, and he'll be lurking outside looking for tourists to convince to part with their fresh new bills for a photograph.