If you wanted a light and fun topic, you could discuss something such as the process of adopting an animal, or the origin of one of your favorite food dishes. You could also do something related to health (the effects of dissociative identity disorder), politics (Should the U.S. restrict immigration?), the environment (What would happen if finite sources were not used wisely?), psychology (what psychological tactics are used in advertising and marketing?), and so on. The possible topics are endless! Just be sure to pick a topic you’re interested in or knowledgeable about, as it’ll help your speech flow smoothly. Hope this helped! :)