I don't know what kind of a speech you have to make, but here are some ideas.
1. Pros and cons of graduation speeches. If you reference Mark Twain's "Advice to Youth" you will get some great ideas and you will be able to make your speech funny. See the reference below.
2. Whether it is better to go to the Superbowl and sit in the nosebleed section or watch the game on TV.
3. Would you travel into outer space in a vehicle that has been built by a private company?
4. Should the death penalty be abolished?
5. Is the fast-food industry responsible for childhood obesity?
6. Is texting affecting the social and writing skills of young people today?
7. Are there any places where phones should be banned?
8. The importance of organ donation or maybe blood donation.
9. Choose a word of wisdom from the "brainyquote" site below and state why you believe it is true or false.
10. Should we keep the death penalty?
I have given you more than the five you needed. Hope this helps you zero in on your topic.