Honorable Mentions:
Fritz - Braindead 13
This one didn't really make the cut for the actual list because his placement as a basic enemy is very... nebulous. The fact that it is from a game that is an interactive movie aside, Fritz is the driving force trying to kill you throughout the game. He is the Igor-like servant of a maniacal brain in a jar, and he has an arsenal of weaponry that's self explanatory.
The only reason I remotely considered him is that he is the closest thing to a regular enemy throughout the game, as all other enemies are found only in certain areas given the game's nature. However, he is SUCH a presence in the game that the covers for the game even say it STARS him, so... I didn't think I could put this on the list.
Fun Fact! The version of the game I have (and possibly all versions?) does NOT have flashing indicators designating where you should probably be considering to go like Dragon's Lair 2. This resulted in me spending over five minutes having THIS happen to me on the first screen:
Splicer - Bioshock
This is a reach because the particular Splicer that sets the tone for the splicers of the rest of the game is actually not fought here at first... it is mostly just for dramatic effect, and the first ACTUAL Splicer fought goes down much easier. However, what it DOES do is create an intensely eerie atmosphere and sense of dread. You are entering a floundering underwater city that is dominated by gene-splicing freaks who have lost all sense of reality. You're boned, bro.
Robo-Collector - Dynamite Headdy
While the next one that actually did make it on the list was sort of a reach for the format of this list as well, the reason THIS one is a little bit of a reach is that the enemy is a unique one. He doesn't appear anywhere else. However, that is generally the nature of ALL the enemies in this game. It's not even as though most of them are bosses, they just appear in one place, usually JUST once, and then they are gone.
I love the enemy because he's bright, colorful, introduced VERY dynamically, and is a good indicator of the kind of design to expect from this game. However, I did not think that this enemy had as much of an impact on me as the other two that are reaches that I included, so... that's that.
10. Sniper Joe Mech - Mega Man 2
This one is only a reach because he's not the VERY first enemy of this stage... that honor belongs to those little turret guys who shoot in arcs to try and hit you correctly. No, this guy is the second type of enemy, but GOD DAMN he goes all out. He's big, he's intimidating, he looks like a badass and he jumps HIGH.
Flash Man was the very first stage my brother and I selected to play when we first played this as kids together. This enemy has gone so far as to influence my style of character design (I love stuff in armor with helmets that have glowing eyes). However, I don't put him higher on the list because he's not the FIRST first enemy of the stage.
9. Pig Soldier - Rocket Knight Adventures
I don't know why, but something about these enemies has just stuck with me ever since I saw them in like... GamePro magazine or something. I never even owned this game, though I had played it a few times, and it is definitely a fun one. The almost pastel colors of their armor and the hilarious way they don't actually die, but run away in embarassment from getting their armor blown off down to their boxers makes me chuckle. Plus they expand beyond basic enemies as time goes on, becoming pilots of miniboss mechs and the like.
8. Zombie - Resident Evil
The FIRST zombie. He's gross, white-faced, caught in the act of eating a comrade, and he's caught your scent and is coming for you.
I played this game with my brother and friends when I was pretty young, and we always made an effort to play these games in the dark. Something about the creepy PS1 FMV and the close quarters you have to fight this guy in just made it feel like such a panic as a kid. Back then I SUCKED at Resident Evil style tank controls, so that made it all the more terrifying.
7. Rabite - Secret of Mana
I always loved this guy. He's adorable, but he's also a MONSTER. He likes to bite, but when you hit him he shields his face with his ears and is like "Why you do that to me?"
The opening of Secret of Mana is one that is very familiar and nostalgic to me, so naturally I often include the Rabite as part of that memory.
6. Warg - Castlevania: Symphony of the Night
This enemy in the grand scheme of the game is very simple. He has low HP, appears right at the start, and goes down easy thanks to your stellar starting equipment. But that's also part of why I like them.
They are made out to be massive beasts, the only sprite larger than them up to this point being Dracula in the flashback before this. Despite their grand nature, you cut right through them, doing an exemplory job demonstrating the power Alucard has before Death strips him of it. That, and it's immensely satisfying to hear that howl and the way they fade away and burn up.
5. Dreglings / Hollows - Demons' Souls and Dark Souls
At first, these enemies don't seem like much, and you're right. A single enemy like them is pretty simple to defeat. That fits perfectly with these games so much: they put you in a false sense of security, and then WHAM! Everything you know is useless as it springs a deliciously horrible trap on you.
Even though they are pretty much nothing to me now, when I first got these games I KNEW they were going to be hard. So I would slink up to these guys and whip them around with my weapon as much as I could in fear of them lashing out at me with a one hit kill that never came. However, throughout the game they come in such numbers and such variety that you'll always be on edge around them.
4. Zebesian Space Pirate - Super Metroid
Super Metroid is one of my favorite games of all time, and these are among my favorite of the basic enemies from that game. I love their insect-like design, as well as the way they are so versatile and climb up whatever they can. Like the Hollows, these guys come in a lot of different flavors later on, so this intial encounter where they take as little as one hit puts you in a false sense of security for later, where they gradually upgrade into near miniboss status.
The atmosphere for their introduction is probably what did it for me the most, though. At first you venture down Zebes until you get the Morph Ball upgrade with not a single enemy being seen. Then you come back through the chamber where Samus defeated Mother Brain in the first Metroid game, and suddenly it is filled to the brim with these guys. I almost panicked the first time I saw them, until I realized that Samus is just too awesome to die to these chumps.
3. Pantheon - Mega Man Zero
I'm a tremendous fan of this series, and I LOVE the design of these enemies. They are based loosely on the build of X, who in the first Mega Man Zero game is now leading a utopian society for humans, but commiting acts of genocide against Reploids. You are ressurected by a group of rebels looking to save innocent Reploids, but they are under attack by these suckers, and even one of these proves to be a lot for them, let alone a group.
So how does Zero handle them? He blows through them with ease, cuts through them like butter, sends parts of them exploding all over the place. The satisfaction of being such a one-man-army against what is supposed to be a rather effective, albeit mass-produced machine of death is just SOOO satisfying. Seeing them slowly cut in half when you use the Saber is one of my favorite features.
Fun Fact! THIS image has always made me wish there was Warriors games for the Mega Man series:
2. Narshe Guards - Final Fantasy VI
FFVI is one of my all time favorite games, among games like Super Metroid. Everyone has a favorite Final Fantasy game (or just can't stand them entirely), and this one is mine. Like a lot of other games on my list, I played this a lot with my brother in an effort to beat it. And this is where you begin: as a brainwashed magical soldier piloting mechanical armor against mummy-soldiers in a far-north town. A recipe for greatness.
In all seriousness, the atmosphere in conjunction with the enemy design is what made me put this on here. The enemies may be weak, but it's what their presence represents to me that makes them more impactful. You're the villain in this moment, and these are (admittedly creepy looking) people just trying to defend their town. Sure, other games have done it countless times, and FFIV before it had this kind of feel for almost the entire first act of its plot, but I like this introduction better. The weakness of this enemy makes it clear that the Empire is a force of death. And minutes after this, you'll be hounded after by them for the remainder of the game... mostly.
1. Foot Soldier - Teenage Mutant Ninja Turtles (Various)
If there ever was a game series that saw a long amount of time in my NES or my SNES, it was Ninja Turtles. Back in the day, I watched the show (so young that I don't even remember most of it), had the action figures, and of course, played the games. Time and time again, this is the enemy you would run into first: the Foot Soldier.
They seem like pretty basic fodder at first, but they are present from beginning to end, and their tactics and even the way they are introduced on screen ups the ante time and time again. They'll come at you with spears, with swords, lasers, helicopters and even riding on the back of dinosaurs. But for me, it all started right here: a building on fire with some silly purple mooks trying to punch you to death.