Prelude (Cello Suite No. 1) by JOHANN SEBASTIAN BACH
The Prelude of the first suite for unaccompanied cello of Bach is probably the most popular piece among all cello suites. It has been featured in films, TV shows, video games, etc. That is— 98% of the time, you've already heard of it, no matter what your favorite music is. :) Hit the link on my bio to watch the full video.