A professor at Hogwarts in the Harry Potter books and movies. Notable because of his dubious allegiance to both the good and evil forces in the story. And also because, contrary to what the author's intentions probably were, some fans find him sexually attractive. The actor Alan Rickman being cast as Snape in the movies may have had a bearing on this.

The guy who kills dumbledore

the bravest man Harry Potter ever knew. The man who love Lily Evans and introduced her to magic. The man who was a spy for Dumbledore and killed him on his orders. The man who was head of slythering. The man who was potions master. The ultimate Slytherin, with the ability to be a sarcastic bastard to harry all the while saving the kid's life over and freaking over.

The very sexy head of Slytherin House at Hogwarts. From Harry Potter

Severus Snape is the misunderstood tortured soul from the Harry Potter series. He is a Potions Master and the Potions teacher at Hogwarts. He is also the head of the great Slytherin House. Severus saves Harrys life over and over again and never gets any thanks for it. He only even loved one woman, Lily Evans Potter (Harrys mom) which is why he protected Harry for so long.

He also must play a role as Voldemort's favourite Death Eater so that he can spy on them for Albus Dumbledore (Headmaster of Hogwarts). In the sixth book Dumbledore asks Severus to kill him since he is dying anyway and he doesn't want Draco Malfoy to have to do it. Severus does it selflessly and is labeled a murderer and a traitor by all the Hogwarts people.

He is sexy and intelligent and a snarky bastard. He is also an only child. Liz C. said that Bellatrix LeStrange and Narcissa Malfoy were his sisters. THIS IS WRONG. They are not related at all they are only his acquaintances.

In the end it is Severus Snape who gives Harry a memory Dumbledore told him to. He was never a bad person, he was forced to play two roles and always wear a mask. He only did what he had to to win the war. And he did what he was told by Dumbledore, the only man who ever showed him any mercy.

The very sexy Potions Professor at Hogwarts. Very sarcastic and arrogent but in a sexyful way.

Absolutely anything you want it to be.
Regional variants include "Snapey" and "Snapey Cormack".
Some say that Snape predates time and space.
Although many have speculated that Snapey is the original Snape, he and Baby Snapey are in fact twins, lending a whole new layer of complexity to intersnape relations.
Some say that all of Snapeism grew from a single snape. The rapid rise and proliferation of Snapeism can be attributed to the incredible speed with which snapes rise to prominence in their local communities. From these positions of authority, snapes preach of Snapeism, and the inevitability of complete snape domination. This phenomenon has been dubbed by leading sociologists as Snapevolution. Snapevolution is thought of in certain circles as humanity's final step towards divinity, and as such is a process to be welcomed and aided whenever possible.
As the author of this piece, I simply offer a heartfelt welcome to the ranks of Snapeism. But for those heretics that wish to remain uninitiated, I have but a single warning:
Snapey cometh.