Molly Grue's reaction to Schmendrick celebrating he was able to turn a Unicorn into a mortal woman.
Schmendrick:(capering happily) The magic chose the shape, not I. I am a bearer, I am a dwelling, I am a messenger!
Molly: You are an idiot!
The sequence where the unicorns rise out from the ocean as a tidal wave.
When the Unicorn sees Prince Lir's Heroic Sacrifice and decides to charge the Red Bull instead of running from it. She is the first unicorn who had something worth fighting back for. To say nothing of when the Red Bull turns and goes into the sea, defeated — and then a HORDE of unicorns comes charging up out of the sea, running all around Haggard's castle... which then falls apart and collapses into the sea, with King Haggard falling to his doom shrieking in bitter triumph, "THE LAST! I KNEW YOU WERE THE LAST!"
Christopher Lee gives us an absolutely perfect Motive Rant as King Haggard too. He Really Can Act does not even begin to cover it. Haggard says that he thought he would die when he saw his first unicorn. I practically died when I heard him describe it. —Speedball
As noted elsewhere, Lee read the book at loved it so much he underlined entire sections he insisted be kept in the film, including the Motive Rant. Without him, it would have been left on the wayside.