My favourite speaking activity is debate. it helped me improve my speaking skill and my knowlede.

Debate activity is suitable with students who are in higher level. This is simply due to the fact that students need to have good grammar, good speaking skill and wide knowlege to express their viewpoints which also let them practice critical thinking. But it shouldn't last too long. It's perfect to discuss a topic in 10 minutes. Students will listen others' opinions and give their own viepoints,  and they disagree with this opinion. they also need to give explanation and example to respond opinions of another's students