Are there any pieces that you find have enough depth and impact to find yourself "lost" in them? By this I mean that they are long enough that you feel a sense of architecture and pacing, that they express profound feelings (either positive or negative), and when well performed can almost completely absorb the mind of the performer and audience.
Some standard repertoire pieces that come to mind for me are Beethoven's last four sonatas, and Liszt's B minor.