Mary Sue

A Mary Sue is a character who is over-idealized, unrealistic, and acts as a wish-fulfillment fantasy for the author. The practice of writing a character as a Mary Sue is almost universally looked down upon and considered one of the worst traps a writer can fall into. Many Mary Sues are self-insertions.

Despite being generally associated with fan fiction, professional and original works have had characters criticized as Mary Sues, such as Wesley Crusher of Star Trek: The Next Generation.

Examples
Note that all examples are highly subjective and in some cases controversial.
 * Dagny Taggart from Atlas Shrugged.
 * DJ Croft, from Neon Exodus Evangelion.
 * Eragon.
 * Marissa Picard, from the works of Stephen Ratliff.
 * Wesley Crusher, from Star Trek: The Next Generation.