I have rejected some candidates simply for the contemptuous or disrespectful way they treated our receptionist when they arrived at the office. Again, there are no time-outs. I've met candidates who have told me that their company was simply the best, that they always knew what customers wanted. Apparently, they just did. I've had people who said they had never made a business mistake.
Nobody's that perfect.
Lack of self-assessment or marketing savvy. When you're trying to sell yourself to an interviewer, know your merchandise. Don't sell yourself short. And I feel uncomfortable selling to people I don't know. Being too officious or assertive.