Yes. I’ve heard, with my own ears, somebody seriously rate themselves higher than 10 out of 10. I'll never forget the claim: "On a scale of 1 to 10, I'm a 13. My SQL Server skills are that good." Of course the candidate was hired (it wouldn't be much of a story otherwise) and the consequences weren't pretty. Years later, the team that made the hire is still trying to overcome the reputation of minimal competence, unresponsiveness, and outright contempt that this individual bequeathed them.
On a lighter note, a little tidbit about the most overlooked risk in software engineering (again, from CodingHorror):