4. Rio Bravo (1959)
http://www.youtube.com/watch?v=v2ssbgThljU You'd think an old western that finds a bunch of dudes sitting around a prison, pulling out a guitar and quietly jamming wouldn't work. I was skeptical, not being a particularly big Ricky Nelson fanatic. But this is Howard Hawks. And Dean Martin. No one could exude class like that man. This scene gives the gang time to recoup, bond, and show off not only the pipes of Martin and Nelson, but the inexplicably capable whistling of Dean Martin.