G-Man, Half Life Series
First seen speaking to scientists at Black Mesa and peering at Gordon Freeman from behind a glass before the whole situation goes to hell, the G-Man plays a pivotal role throughout the Half-Life series of games. From waking up Gordon Freeman from his deep slumber at the start of Half-Life 2, to speaking with various characters that Freeman encounters throughout the game, the G-Man is as ubiquitous as he is illusive, causing players to suspect that he is pulling the strings behind the events that happen.