Weird that you posted this. My wife and I just finished a documentary on The Bee Gees (yeah, I know), and when they played Stayin’ Alive, I commented about how the opening scene of Saturday Night Fever was so iconic.
But to answer your question, I’ll go with the Usual Suspects and every Tarantino and Kubric film.
usual suspects is a great suggestion as the opening really doesn't give you an idea or where it is headed.
early tarantino yes because it was new, but his movies seem to have fallen into a set pattern similar to robert rodriguez. tough to continually reinvent and not fall back to what is comfortable.
similar to guy ritchie movies. snatch starts out with a strong start that doesn't give away the direction of the movie, but his work since that either has been a bit bizarre as in his take on king arthur or rooted in his gangster formula
good call on supertroopers ron,
star wars was different from everything else, but you could get a sense of where the movie was headed, same with the town and the dark knight. you could see where both of the movies were headed fairly early.
the wild bunch is a great movie tetonfrog, but as with some of the others the start pretty much is taking you in the direction of the movie.