Game developers have found numerous ways to thwart heroes on just about any quest dreamed of. The marine in Doom found himself flailing again and again against hordes of pinkies, imps, and cyberdemons. Even the block holder in Tetris finds itself forever filled with block after block with no hope in sight. Each genre has its share of nasty and annoying opponents.
Action games are renowned for their epic and over the top boss fights. Ask any player that has slain Mundus in Devil May Cry, or waged battle against slinky Alma in Ninja Gaiden what they remember from these games and most certainly the answer will be: the boss fights. Even in games days past there is certain fuzziness to people’s memories of the normal enemies within their favorite action games. It would be a sin to forget that leading up to that climatic clash between good and evil, there is a whole ocean of cannon fodder to be dealt with.
When an action title’s basic forces are uninteresting and easy the underpinnings of that title are ruined from the start. In order to enjoy the battle at the top of the head the player must enjoy the frantic climb to the top. In a time when enemy AI was only a programmer’s dream the only way to instill respect into a common enemy was pattern. The classic pattern of many action games was the up and down wave where an enemy approaches from one side of the screen at a given speed. Sometimes this behavior would be a perfect sine wave but other times the enemy would change speed or pitch to throw the player off. Many of these creatures have become iconic within their franchise precisely because of the challenge they provided.
Medusa Head – Castlevania

The medusa head in Castlevania is perhaps one of the most deadly sine wave enemies ever made. Featured predominately in the series, the medusa head is often followed by frequent cursing at her first appearance. This is because despite her lack of any defense (she is typically defeated in one crack of the whip) she is positioned for one purpose and one purpose alone: to knock x y or z Belmont to his death in a nearby bottomless pit. Her spawn forgiveness is practically nil which forces the player to not make second guesses when getting through a dangerous jumping section. Jumping, already a stiff action in the older Castlevania games, becomes a life or death action when a medusa head is added to the mix.
Despite the ease of the post-Symphony Castlevanias, medusa heads have gained a new foreboding trait: the ability to turn the player to stone. The joy of leaping to and fro easily in Castlevania: Symphony of the Night can be stopped abruptly by a yellow medusa head turning you to stone dropping Alucard to his death atop a row of sharp spikes.
Unicorn Head – Zelda II

Zelda II is the black sheep of the series not only because of the game play style, but also because of the title’s bizarre arrangement of enemies. While the standard flying bats and sword wielding skeletons were present, they took a backseat to dead fish heads and walking piranha heads. The most annoying of the flying sect was the unicorn head. What appears to be a severed unicorn head with a blue almost iguana-like frill is a constant pain in Link’s side.
Unicorn heads almost universally appear over bridges. In a crumbling temple, the player can rest assured that most of the bridges have breaks. Whether it was lava, water, or simply the endless darkness of space, the unicorn heads have it out to knock Link off of the screen.
On top of the speedy sine wave pattern, the unicorn heads are much more resilient to punishment compared to the medusa heads. Several hits are required to destroy them. That also says nothing about their spawn forgiveness, which was some of the worst in the genre. Scrolling back and forth would force the game to send 3 or 4 unicorn heads directly at you, all flying at slightly different distances from each other. Woe to the Link that decides he can slay one fast enough to avoid the second as that almost never goes according to plan.
Ball Elephant – Mega Man 9

Mega Man 9 has made quite a splash in the few days it has been out. The general consensus is that Mega Man 9 is one of the most difficult of the entire lot, lending itself to many one hit kills. As this writer played happily through the 8 robot master’s stages, one enemy in particular stood out as be baffling annoying: the robot elephant.
Reminiscent of the large wolves from Mega Man 2 the robot elephant is one of the most defensive enemies in the game taking many shots to put down. What would usually take short order can become quickly hectic, as the robot elephant begins tossing his giant red ball at you. The last meeting with the robot elephant ends in a room with multiple gaps in the floor. As the red ball comes bouncing erratically up and down towards poor Mega Man he must find a way to pop off a few rounds into the elephant. Quickness is essential because as soon as the red ball finds its way to the left of the screen the elephant will suck in with his long trunk pulling the ball AND Mega Man back with him.
This creates something in Mega Man 9 that cements it as a return to form. It introduces a new pattern never before seen. The player must have quick reflexes to either jump or walk under the large bouncing ball, fit a few shots in while doing so, then be ready to walk against the elephant’s trunk suction and avoid the ball’s return! All of this while staying in place to avoid a quick trip into the officially NES-licensed pit of doom.
Waver - Metroid

In a trippy game such as Metroid, with its surreal music and otherworldly environments, the developers saw fit to even toy with the basic sine wave pattern. Wavers are the Venus fly trap looking critters that float lazily to and fro, simply rough-housing Samus into the lava.
The wavers pattern of falling and rising has a small bit of randomness in it as the beast will sometimes drop far lower than expected, only to elevate at a brisk rate a few seconds later. Wavers fall into the same arena as unicorn heads. They are tough to kill and spawn mercilessly. Add to this that the horizontal rooms they inhabit are much longer and slower to get through than any straight bridge in Zelda II and Samus will find herself being hounded by the same waver at different intervals.
Dealing with a waver is the same way Samus must deal with most of her opponents: calculated diligence and firepower. The player shouldn't be afraid to waste a missile or two knocking these bad boys out of the air.
Koopa Paratrooper – Super Mario Bros.

Eager children firing up their copies of Super Mario Bros. for the Nintendo Entertainment System were overjoyed to smash koopas into their shells only to send them hurtling to their deaths with a vicious kick. It didn’t take long for the koopas to wreak their own revenge. Late in World 1 the koopa gains a new trick: a set of white feathery wings. Hopping up and down, eagerly looking for a fat Italian plumber to send hurtling to HIS death, Koopa Paratroopers are a staple of the franchise. What was originally a slow moving makeshift weapon, suddenly turned into death from above. Perhaps one of the most unsettling aspects of the koopa paratrooper was the reptile’s penchant for suicide. It didn’t matter to the creature if it had to go plummeting to its own death from atop a giant mushroom, as long as it took Mario or Luigi with it. Even knocking the hero from super to normal size would be worth the sacrifice.
It is hard to admit defeat at the hands (or feet or maw or whatever) of a boss in any game. Even harder to admit is the ignoble defeat by a minor enemy. So… just don’t admit it.