Honestly, I've got a group of friends that are not only intensely interesting, but are intensely interesting in very different ways. Some fiercely unique minds. I think I'd have an easier time telling you what my favorite song is.
Then view this question as an opportunity to practice your descriptive skills. I would love to say that I have some intensely interesting friends with some fiercely unique minds, but that's more of an appeal for the audience to simply believe the author. There's no demonstration of fierce uniqueness. Reminds of a common writer's tool. Show, don't tell.
You've immediately unveiled the flaw in the question. That said, I'd be interested in hearing what makes some of those friends minds fiercely unique and would suggest to others seeing this question to not make it in to the competition that the initial question begs, but rather a way to celebrate some of the wonderful people in our lives. edit: But yeah, what's your favorite song?