Lately I've been reading Yes!: 50 Scientifically Proven Ways to Be Persuasive for the second time. A lot of what the authors include makes a lot of sense to me. One chapter in particular stood out to me. The main idea of the chapter was that you can use your weaknesses to your advantage to make them into strengths. And by that, I don't mean in the cliche interview question response kind of way (my biggest weakness is that I work too hard and care too much).

Rather, this concept is best used to portray authenticity and honesty by exposing a part of you that is less than stellar. Consider the following examples

Progressive's campaign to inform potential customers of the lowest price for insurance, even if it's from another company.

Avis car rental's slogan "We're #2, but we try harder."

One of the old Volkswagen Beetle's campaigns "It will stay uglier longer."

Naturally, one caveat to this is that the weakness you expose can't be so significant that it completely turns people away from what you are offering. But properly played, I think that this tool can be effectively used to show people that you are just a regular person (or company) with regular faults. Of course, if you can follow your shortcoming with one or three or ten reasons why you are still amazing, then you'll have a better shot at being persuasive.