Psycho Mantis from Metal Gear Solid. This game broke boundaries in gaming, and nowhere more so than in this boss battle. Before the battle even begins Mantis demonstrates his mind-reading and telekinetic abilities through clever use of the PSOne's hardware. And if you're not expecting it, it's actually quite intimidating.

Once the battle starts things get even stranger. Try as you might, Mantis seems impossible to hit. He predicts every one of your moves and dodges the bullets accordingly. Only by switching your controller from port 1 to port 2 can you thwart his mind-reading and stand a chance of victory.

While the combat itself is quite straightforward, Psycho Mantis is a great boss for completely different reasons. Some enemies have a huge gun or heavy shielding, but the player knows that by learning the attack patterns or through skill and dexterity these obstacles can be overcome. With Mantis, this isn't the case. Even in the game world his powers are unusual, and his ability to confuse and frighten the player makes him a truly formiddable foe.