The one that bugs me is people who describe themselves as just 'consultant'. I've met two of the following.

Yes, a consultant, but what kind? 'I'm a consultant' Yes, but what do people consult you for? 'For when they need consulting' Yes, but about what? Are you a medical consultant, a security consultant, a civil engineer, a financial consultant, legal, something else? [puzzled look] "I'm - a - consultant."

Boring conversation anyway...