Dark Roasted Blend has an amazing collection of stunning and interesting trees right now, including the African tulip tree above, which is apparently very invasive. With a tree that pretty though, I don't think I'd mind if it took over my whole neighborhood. How about you?
Link
Unfortunately, they also grow REALLY fast, are quite large and their seeds fly off and grow almost anywhere.
I've had them sprout in cracks in the concrete, in the middle of a dense Camellia hedge and in the driveway.