9. Psycho Mantis
Game: Metal Gear Solid (1998)
There is no boss list complete without this entry. Resident psychic, sadist and creeper Psycho Mantis tripped the minds of players with some sly gaming tricks even by today's standards. Mantis broke the fourth wall (more like kicked it in) by switching control layouts on controllers, blacking out the screen and making comments about data on your PS2 memory card. While fighting the metal giants later in the game was difficult, this psychic encounter is far more memorable. No other boss has hit that level of awe in gaming history.