What are tough questions in interview process?

Here are only a few of interesting questions that I collected on the internet. Pretty many so you can find out more on this link:
http://www.gowrikumar.com/interview/index.html

1. What other firms are you interviewing with, and for what positions?
2. Do you believe you're overqualified for this position?
3. What would you do if one of our competitors offered you a position?
4. What's your dream job?
5. Tell me about a time you didn't perform to your capabilities.
6. What color is your brain?
7. Give me proof of your persuasiveness.
8. What environments allow you to be especially effective?
9. Whom did you choose as your references and why?
10. Now that you've had a chance to learn more about us, what would you change about our company?
11. What type of decisions do you have difficulty making?
12. What are the major reasons for your success?
13. Tell me something about yourself that I didn't know from reading your resume.
14. What have you learned about our company from customers, employees, or others?
15. Why weren't your grades better?
16. Would you be able to work extended hours as necessary to perform the job?

What is your benefit for company?

When I join an interview with Stand Charted Bank in Hanoi around years ago. I still remember this tough question that Director give to me: Give e a reason why we should not hire you.