* The scene where the view screen is destroyed and Picard and company can see Shinzon's ship through the hole in their hull. They conveyed a real sense of danger to me that Star Trek rarely did.
*The concept of the Remans. The Romulans have a secret off-shoot race they keep as slaves -- or just a slave species, in general. Since the Romulans are known for their secrecy it actually makese sense that this would be a little known fact in the Trek universe.
*Riker's words at Data's funeral. I realized that I couldn't remember the song he had been whistling, either, and it made me feel horrible.