What are some good songs to sing for 11 year olds?

Im 11 years old and I think I have quite a strong voice, I have entered a talent competition and came 2nd place. I have applied for an audition on Britains Got Talent and hope I get in. But I'm stuck by what song I should sing! Has anyone got any good songs that I could sing? Oh yes, and pleaseee dont give me easy songs or underestimate me because of my age, because I actually do have a very powerful voice! Thanks everyone!!! x