This is a depiction of one of my many D&D characters from long ago. His name is Simon Stromnos. The sword in his back was cursed by a witch and magically fused to his back after she hurled it at him. He survived due to wearing plate mail armor, however the witch did not survive his ensuing wrath at being stabbed in the back. The sword causes no pain, nor is an immediate threat to Simon's health, however it is pretty damn inconvenient to have a sword permanently sticking out of your back.
The sword has been used for his advantage, and unfortunately on occasion to his enemies' advantage. It can be used to hoist Simon up or down, or to throw him in a specific direction. It can deflect blows, as well as cause damage in the right conditions.
During the course of play with this character, we did pretty much all of the above when it came to utilizing Simon's unique talent. Other than that, he was just a mercenary, out for adventure and gold.