14 'Genius' Video Game Features That Were Total Accidents

8. The Spy Class In Online Shooters

What you think: The spy class in online multiplayer games is just one of the base options that's evolved in various machinations over the years into everything from Team Fortress to Battlefield, Halo and Call of Duty, letting you infiltrate the enemy's ranks without being seen, turning the tables from the inside.

What actually happened: Team Fortress actually came from iD Software's Quake engine; a maelstrom of modded content and talent on behalf of a dedicated programming team headed up by one Robin Walker - rather like Counter-Strike branching off from Half-Life. They set about creating a slew of new classes for their game, but didn't account for one that would accidentally mimic the skin of the opposition, naturally resulting in players on the opposing team holding their fire.

Such an idea was brilliant in of itself, and following Walker's hiring by Valve and their team overseeing development of a fully-fledged independent sequel, the Spy was given the same proper character and loadout treatment as everyone else. It's pretty crazy, and means you could almost say the game spawned one of its most popular archetypes all by itself.