Palpatine's seduction of Anakin in the chamber after the performance. There was some bizarre sexual undercurrent to that scene. Something along the lines of a perverted, powerful old man trying to ply a young kid. First, he played on his trust and feelings of loyalty, told him not to say anything to the grown ups, then he mentioned the dark side in passing without moral judgment, then finally asked the kid to put out, all while looking simply pathetic- "yes, I know I am awful, and you should rat me out..."
That scene just made my skin crawl. If the parallels I just mentioned were there on purpose (and I think they were), all I can say is that it was perfectly written and directed by GL, and expertly acted by McDiarmid. Evil, evil, evil- that scene sold me on how thoroughly rotten Palps was. Ugh- makes you want a cold shower.