This is a fantastic video from Scottish star chef Gordon Ramsay about cooking the most simple of things: Scrambled eggs! There is an interesting moment when he says: “we always ask new chefs in the interview to cook scrambled eggs. And if they know how to cook the *perfect* scrambled eggs, then you know they can cook properly!”.
Most people will come to interviews mentally prepared for highly complicated tests related to their skills and expect the worst. You can throw them off-guard and see how well they think on their feet by asking them to do something extremely simple. How they handle something as “easy” as cooking eggs can say a lot about whether they are the right person for you. Are they able to put as much love and effort into simple but regular tasks? Or are they only interested on being “rockstars” in everything they do?
If you interview an extrovert candidate who seems clearly confident, then why not ask them to tell you a joke. But stay flexible and have several scenarios available for different types of people and choose the most appropriate for a person on the fly. Never leave them gobsmacked or uncomfortable because it will leave a sour image on you as a person and the name of your company.
Using simple strategies can be much more rewarding than grilling them with thousands of technical questions. Drawing your candidate out of his/her shell is essential if you really want to “work with them”in later stages of the interview. Many employers invite candidates more than once. They use the first interview to break the ice and as a general introduction and the second one to go deep into practical applications.
Is your firm thinking about bringing in a new hot-shot, PMP® certified senior project manager who mentioned “cooking” as one of his “hobbies” in the CV? Then why not take them out of their comfort zone and to your office kitchen where you ask them to cook “a full English breakfast” for 6 people! If they can put the food on the table for everybody at the same time, while still hot and without a microwave, then s/he is your guy! 
Are they heavily into Mountain-Biking? Give them a bike and ask them to change the tube of the tire as quickly as possible. You can do a lot here with the listed hobbies since this is what they really love and should therefore be passionate about.
So unless you are the director of a circus, please always judge by the effort made and not the results when asking to do something they will never actually perform on the job! 
What are your favorite interview techniques or what were the questions people asked you in the past?