Which of these songs would be good to sing in a talent show?

It really depends on which one you do best, but I'd go with Say by John Mayer or I'm Yours by Jason Mars personally. I'd skip the Miley Cyrus one. Nickelback is great but not really talent show material unless you've got a band and can do it justice. I haven't heard the Sean Kingston one and it might not be a good if it's not something people are familiar with.