I. What is a Mary Sue?
A Mary Sue is a common term that can be seen and found in any fandom. I find that a Mary Sue is usually an OC, or original character. However, there are several cases where the Mary Sue is a canon character, a character from the actual series the fandom is centered around. A Mary Sue is, simply put, a perfect, unrealistic, idealized character with too little negative flaws that can be exploitable or cause any misfortune to said character.
If your character is accused of being a Mary Sue, don't fret yet. Take a moment to analyze your character. I will type about how to identify and a step-by-step manuel about how to perform a Mary Sue Surgery. Let's first start with what kinds of Mary Sues there are before deeming if the OC you have is a Mary Sue.
II. Common Mary Sue Types
There are several types of Mary-Sues. If I try to list all of them here, this wouldn't really be an introduction to Mary Sues.
The Perfect. This species is identified by noticing gorgeous flowing hair of an unnatural color, without dying it, eyes that can "stare right into your soul," and the perfect body that makes every girl hate her because of how flawless she is. She usually has every character fall in love with her, become OOC, while being better than them in everything.
The Goth/Emo. These species typically wear black, shop at Hot Topic, and cut. Their parents are mostly likely dead, they have been abused and raped multiply times, and they seek refuge in the arms and bed of the canon character of their choice. One excuse is see for falling in love with a canon.
The Self-Insert. This type of Mary Sue coincides with the Anachronistic. This category of Mary Sues are typically the author in the disguise of an OC. The two characters have the same fashion, likes, thoughts, ect. to the point where you should consider them the same person. Fanfictions that send said character back in time or into the world of their favorite fandom. If they aren't an exact copy of the author, they're a better copy of them.
The Badass. To identify these species, they possibly have some sort bad past, are on a journey, athletic enough to win every gold medal in the Summer and Winter Olympics, with a crap load of weapons. They can often take on the best of the best and beat them at their game, after only a day or two of training.
The Anachronistic. A.K.A. the time-traveler from present day (insert city) that can bring their laptop back to the 18th century, or the wizard/witch that hangs out with the Golden Trio and knows how to use their iPod at Hogwarts. They usually wear a sort of brand or type of clothing that is unavailable in their country or hasn't been invented yet and saves the day or changes the plot with their medical knowledge from the future.
III. Famous Mary Sues
These are just the opinions I find online. To be honest, a good amount of these characters aren't Mary Sues. They're merely characters with some Mary Sue traits. Please don't hate on me.
Name: Ebony Dark'ness Dementia Raven Way
Habitat: The Harry Potter fanfiction, My Immortal by XXXbloodyrists666XX
Type: The Perfect, The Goth/Emo, The Self-Insert, The Anachronistic.
Notes: I will include a link to the fanfiction in the description.
Name: Bella Swan
Origin: The Twilight Series
Type: The Perfect, The Self-Insert
Notes: For those of you who have't read the book, Bella Swan is clumsy in a "cute way," is caught in between a sparkly vampire and a werewolf, and when you compare Stephenie Meyer to Kristen Stewart and Bella Swan's description, you'll see the comparison. She is part of the BAMF Girls Club.
Name: Lisabeth Salander
Origin: The Girl With the Dragon Tattoo
Type: The Badass.
Notes: For those of you who haven't read the book, Lisabeth Salander is an expert hacker, who grew up as an orphan. She is part of the BAMF Girls Club.
Name: Pippi Longstocking
Origin: Pippi Longstocking
Type: The Perfect.
Notes: Personally, I don't really think Pippi Longstocking is Mary-Sue because she was created for the entertainment of children.