We totally called it. Way back when the Iron Man armor mod came to GTA V, closely followed by the massive Hulkbuster armor, we said that all we need now is an Incredible Hulk mod for the epic showdown which comprised most of the marketing for Age of Ultron. Then, when the Incredible Hulk mod was actually released for GTA V, we once again said that now all that remains to be done is for someone to put the two together and, voila!

Well, it took a heck of a lot longer than we expected, but finally GTA V's players came through with a short video made using the Rockstar Editor, as well as the two mods.
In Avengers: Age of Ultron, Scarlet Witch, while still aligned with Ultron, possesses the Hulk to turn against his fellow Avengers while in Wakanda. The big green beast then went on a destructive rampage through a nearby city, prompting Tony Start to activate project "Veronica", the fail-safe system in the case of the Hulk losing control.