A Race? Thats a tough one...
Maybe the Coldains (Thurgadin/EQ), cause they are kinda scary and friendly (if you have enough faction, hehe). Or Drachnids (Firiona Vie/EQ), cause they where fast and scared me like hell. Giants also. It was so much fun, back then, hunting them, with Friends. Or ... two many... idk, hehe.
Beholders! They were epic and scary back in my D&D tabletop days. We had a dungeon master who created some truly vile beholders that, while not as big and scary as dragons, carried the same gravitas. We were truly afraid whenever we found out our archenemy Beholder was behind some nefarious plot.
Honorable mention goes to Rakshasa because I've never seen them used in an MMO. A castle or keep run by a Rakshasa with a ton of illusions, tricks, and traps would be super fun. They're under-appreciated but can be so manipulative and cunning. They were an NPC that I always liked to torture parties with when I was on the other side of the table.
In MMORPGs. I think my favorite NPC race might be the drug dealing Khajit from Elder Scrolls Online. Seedy NPC merchants add a lot of character and realism to a game world I feel. Underhanded deals and shady back alley trading add a very lived in feel to any game world.
I have a few favorites.
Giants - Cause they seem to have better loot in general, and you get a sense youre killing something epic.
Skeletons - Classic undead NPC. I think every game needs them.
Sarnaks and Goblins - I think I killed these the most through my own personal adventure, fighting them either in castles, dungeons, or whereever so they're the most memorable to me
Dragons, even if it's a rare race.
Certainly because of Nagafen in eq2, the trip to talk to him was hard, he was quiet deep in a dungeon. I love their terrifying noble and superior ways, in front of a dragon you know you're in danger each second even more if you're talking with him. He was magnificent, moving like a snake and didn't hesitate to one shot you if you said something bad about Lady Vox. One of the rare NPC with who you need to choose carrefully what you hit in the dialog box, you know that the moment is important. Actually in my guild there was a contest, the nagasmash, it consisted to record how many damage he done to you.
OMG, way, way, WAY too many to pick a single favorite.
The original Orcs in Greater Faydark have a very sentimental value to me.
Similarly, the Goblins of Illomen were simply amazing - new, unique, scary and cool looking.
The sirens from TBS were the most artistic monster model and very much in-character.
The M'sha's out of Qvic, goats!
Also frogloks, I never got tired of killing frogloks.
EQ1: Coldains / dwarves - Their appearance, their ice city (Thurgadin) and building structures within. I have fond and funny memories of my ogre trapped inside their buildings begging for shrink pots before I got my cobalt bracer. Language and faction.
EQ1: Kael / giants - Again their appearance, their city with everything sized for giants (Kael Drakkel). It was my first real sense of awe in terms of scale. Language and faction.
EQ1: Dragons - Because dragons! Again, deep lore involved, dragon language, faction, etc. My first dragon kill was Trakanon and a raid I won't ever forget. I've done many raids in games since, long forgotten about, however this raid (I did many years ago) is one of the few that has stuck with me over the years.
EQ1: Gods - Along the same theme of deep lore. When you finally came across them for the first time, it was a sense of awe.
Part of what made NPCs and their races memorable were not just the NPCs themselves, rather their surroundings (weather, buildings, terrain, etc), their associated music, ambient background noises, languages they speak, if they align with you or against you, and the lore (without lore, things can be soul less, lore is the soul of an npc within a game and to a larger extent the soul of the game as a whole).
I'm hoping to come across an NPC race and for a minute forget it's a game and with all the layers existing at once, feel they're alive, they're actually existing in this world before I came and will after I leave. So many games feel like NPCs or races exist to fill a need, rather than a need filled around the race, like an after thought.
An example of layering is giants where their tables and chairs are massive to us and normal sized for them instead of just having giants in a random cave. It makes it more "believable" like they eat, and sleep, maybe not at the moment you're seeing them but at some point. It adds to their depth, immersion, and that these entities are alive. Maybe Ogres of Oggok where it looks like the flintstones and the swampy areas outside their "city", elves with their magical fonts and buildings, wood elves up high in the trees, etc. This is what made EQ1 races and places memorable for many years.
Races and lore in my opinion are vital to build off, everything is largely built from both, absent of both is existing just to exist as if to fill a gap. It's subtle, but you can tell in many games when you come to that outpost, city, race, etc that just feels it's there "because we need it there to get quests" than it's there because it's part of the world and it happens to have quests/lore. This tends to be pretty common in free-to-play games (not all, but a large number I've played seem this way), NPCs and races exist for diversity purposes alone tending to be generic and vanilla where they usually just exist to hand out an XP quest.
I love the Kurashasa and the Khajiit because I am a crazy cat person. <3
Honorable mentions are brownies and redcaps. I had a great laugh when I encountered grave brownies for the first time, and I had another laughing fit when I discovered a storehouse full of maniacal and homicidal redcaps. It really boggles in the mind in an endearing sort of way to reconcile their tininess with their insane and troubled genius.
