- Mass Effect:
- The game has the Geth Repair Drones. They do not attack, and are only capable of repairing their Geth allies. They only appear once on Noveria, and are never seen again.
- The Mercenary Adept on Presrop is the only one of his kind.
- The Rachni Brood Warriors only appear in one non-essential sidequest.
- Mass Effect 2:
- The game has a technician. One technician. You fight him during Jack's recruitment mission, inside the room where the switch to release Jack from her cell is. He has the dubious honor of being by far the weakest enemy in the game—he has ridiculously low health, has only low shielding on higher difficulty levels, has no powers, and wields the weakest pistol in the game. Even on Insanity, you can pretty much defeat him by walking up to him and punching him in the face a couple of times (assuming your squadmates don't get him first).
- There are also only two specific Krogan enemies who don't use shotguns (they use Carnifex pistols) and have energy shields instead of biotic barriers. One, the Bounty Hunter, is encountered during Thane's recruitment mission, and the other, Kalusk, is found in a sidequest. The Bounty Hunter is particularly notable, as he's the only krogan found working with Eclipse.
- The Geth Recon Drones return from the first game, but now they only appear in one level, Tali's recruitment mission.
- Five freelancers with no ties to any of the game's three main mercenary groups appear at the beginning of Garrus's recruitment, then never again.
- Many enemies which are just reskins of the common and generic "trooper-type" enemies appear in only one mission, appropriate to the context, and nowhere else. Examples include Batarian Troopers, Sisterhood Initiates, and Prison Guards.
- Mass Effect 3:
- The game has three examples of this related to decisions earlier in the series. In the second game, if you betrayed Samara for Morinth, then Morinth appears as a Banshee on the final mission. Also in the second game, if Legion was given to Cerberus instead of recruited as a party member, it is encountered as an enemy at the Cerberus Headquarters. In the third game, if the Grissom Academy mission was never completed, Jack will be indoctrinated and killed as a Phantom, also at Cerberus HQ. All of these enemies are identical to regular enemies gameplay wise, with the only difference being their name and, in Legion's case, a different model.
- Geth Pyros are surprisingly rare in the third game's main story, especially since they approach Goddamned Bats level in multiplayer. Aside from a one-off cameo, they only appear in one mission during the third game, and a side mission at that. There's a grand total of eight of them in the entire game (out of the literally thousands of enemies you kill) despite being no tougher than the other common Elite Mooks you slaughter by the hundred. Like other geth enemies, they don't appear in the downloadable expansions, either.
- Mass Effect: Andromeda:
- The Behemoth, conditionally. If you choose to save the krogan captives on the Archon's ship, you only ever have to fight the one. Save the salarians instead, and you'll have to fight two more later on in the game.
- On Elaaden, there's an asari biotic with a unique name... and that's it. The characters don't acknowledge her, she doesn't speak, and the game never mentions it again.
Unique Enemy / Mass Effect