I think my favourite Horner score is Wrath of Khan. There are so many good parts to that score but the emotion in the piece as Kirk runs through the Enterprise to engineering sets up the scene that follows beautifully.
I have a number of his scores; Star Trek II and III, Rocketeer, Apollo 13, Titanic (which, I hasten to add, I always stop before Celine kicks off!) and Sneakers.
He leaves quite a body of work. A good legacy.