Norway 2010, without a single doubt! And I would even say this is not only the best interval act ever, but also the best moment ever in Eurovision!
No other interval act had until that day (and still until today) the meaning of this one! I cried for the first time I watched it and it still melts my heart. They got the real meaning behind a show like Eurovision and they were capable of expressing it through such a simple interval act. Just some people dancing the same dance in some european cities and some families jumping on their couches! It was just the best!