Halo is a multi-billion dollar science fiction video game franchise created by Bungie and now managed by 343 Industries and owned by Microsoft Studios. The series centers on an interstellar war between humanity and a theocratic alliance of aliens known as the Covenant. The Covenant are led by their religious leaders, The Prophets, and worship an ancient civilization known as the Forerunners, who perished in combat with the parasitic Flood. Many of the games center on the experiences of Master Chief John-117, a cybernetically enhanced human super-soldier, and his artificial intelligence (AI) companion, Cortana. The term "Halo" refers to Halo megastructures: large, habitable ringed structures, similar to the Orbitals in Iain M Banks' Culture novels, or author Larry Niven's Ringworld.

Hitman is a series of stealth-oriented third-person shooters developed by Io Interactive and published first by Eidos Interactive and then Square Enix when it acquired the latter.

Developed by Valve Corporation, the Half-Life franchise is a highly celebrated series of award winning first-person shooter titles which have consistently influenced future FPS development with their unique storytelling methods, such as a constant first person perspective, and gameplay mechanics such as Half-Life 2's Gravity Gun.