- An investigator who is equal parts Hercules and Sherlock Holmes. Nothing phases him. He's at ease whether solving a riddle or taking on an entire bar's patrons in a fight... single-handed. No, literally. He had one hand tied behind his back during the fight, and won without anyone else landing a blow.
- A school teacher with the patience of a saint and a night life the celebrities are in awe of. Whether it's teaching basic reading skills or tossing back shots, this teacher is miles out of anyone's league.
Still, it's good to have some balance to your characters. Make the investigator have a brilliant mind, but be terrified of confrontation. He never solves his mysteries in person because he's too afraid of getting hurt. Or, the investigator could be strong, but he's always a few steps behind the villains. His sarcastic sense of humor gets him into trouble, his fists get him out of it, and his contact in the local police force shows up in time to save the day and clean up.
The book I'm working on writing now "Paradise Found" has a Mary Sue, but I'm tempted to keep him around. The secondary main character is Michael the Archangel. The more famous stories about him are all about physical prowess. This is the being who defeated the devil once, and is ready to do it again. Less well-known stories claim that Michael is a level-headed healer, more intent on helping people overcome their internal battles with evil than with bringing his often-depicted sword to bear on a problem.
The only thing that makes it okay to have such a competent Mary Sue as a character is that my main character is an equal counterbalance to Michael's accomplishments. The main character, Joe Carrigan, is past his prime, doubtful about the afterlife, and mostly just going through the motions. Carrigan is a good cop, and a good man, but only out of sheer habit. Michael can serve as a driving force in comparison to Joe's tired indifference.
For today's writing prompt, try creating your own Mary Sue character. Then, play with the traits to make that character more believable to your readers.
Have fun, and keep writing!