Depends on what you mean by "snowflake". If you mean a simple "LOOK AT ME!!!" attention whore type character, well that would be anything made by those said players

(In SR, just about any archtype and meta-variant can be made into an attention whore character:P)
If you mean "Snowflake" as in "So unique as to not feasibly be a Runner..." well, that is going to vary from person to person... but to get the list started, I'll give you my top 3, in order, and why...
3: Shifters.
Yes, the entire kit and kaboottle. Every single one of them. The problem isn't with Shifters per say (as they are a nifty piece of lore in the world), its characters based off shifters. The number one problem I have with shifters is that people can't read the first paragraph on them (for 5e anyway)... Shifters are
NOT "People that turn into animals", they are
ANIMALS that turn into people. But that is not the way any character I have seen has build them.. nor are the players
playing them as... They are basically... to put it diplomatically, the playground of furries, and furry adjacent.
2: Pixies.
Well... I started it so... Why the fuck anyone thinks something the size and weight of 6 month INFANT is viable in a combat role is just beyond the realm of intelligence. Standing a whopping 1 FOOT 6 INCHES tall (50 centimeters!), and weighing in at 20 pounds soaking wet doesn't stop the "intellectually challenged" from trying to justify everything from "Pixie heavy machine gunners" to "Pixie martial arts"... Which just invokes the image of a the Chihuahua being punted for a field goal, in terms of actual use. With the most common defense being: "Well, the book doesn't mention Physics or gravity, so..." Which goes over as well as a wet fart in a crowded elevator. (And that was me being polite on the topic!)
1: AI.
Again this is something that should have stuck to the realm of NPCs... The level of contrivance that goes into the old AI builds was just beyond the pale... 7/10 of the builds required someone else to carry some "Special" device (usually a commlink) because without it, the AI was well.... useless (and immobile), 2/10 relied on a some "special" drone that usually broke the build rules of the time, but was needed because without the "special" drone, the AI was, well, useless and immobile. Rarely was there an AI build that didn't fall back on the "special" device/drone.. and those builds were generally so weak, that the troll Gunner with 1s in all mental stats was a better hacker... And this is on top of the fact of RPing issues...
There are more... lots more.. But those are the top 3 for me... followed by the infected they come in fourth... Mostly because,
Every. Single. Character has the exact same basic backstory... "Yea I'm infected, but I'm not bad... I'm just miss-understood and unloved. Please, love me and pay attention to me!"
No. you are fucking monster that exists by eating the souls (Essence) of your victims. Stop bullshitting me, and yourself. Besides Anne Rice to Christopher Golden has done the "remorseful Infected" plot line much better than you could.