Crowning Music of Awesome: Also Sprach Zarathustra. Even though it wasn't created for the movie. Also the Blue Danube Waltz and Gayaneh Ballet Suite Adagio, with all three pieces achieving their latter-day fame through their use in 2001. In fact, they were only supposed to be stand-ins for actual movie music before it was ready for release, but they were deemed so fitting, they were left in.
The Requiem that plays when we see the monoliths.
Dave getting from the pod back to the ship, without his helmet.
The story begins with a tribe of apes who are easy prey for rival tribes, and leopards. Then the Monolith teaches them about tools, and the next confrontation goes a lot differently.
The scene where an ape discovers how to use a bone as a tool and uses one to obliterate a skeleton would just be "cool" if "Also Sprach Zarathustra" wasn't playing as BGM. It goes from cool to legendary.
You have to admit, HAL's revelation about how he knew Dave and Frank were planning to shut him off is pretty awesome Dave and Frank had their conversation in one of the pods and made it so HAL couldn't hear what they were saying. What they didn't count on was that HAL was reading their lips.
The Stargate. Imagine the sky simply opening and you find yourself barreling down a tunnel made of streaks of light in colors the human eye wasn't meant to see. And you start going faster and faster and faster...