4. Klingon B**tards
I'll say it right now. Ricardo Montalban's Khan will ALWAYS be the best Trek villain. There will never be anybody better. Period. Any attempt to do better than him will fail. The best you can do is try to make a good villain. And the Klingons in "Star Trek III" were pretty good villains. Christopher "Doc Brown" Lloyd was an interesting choice to play the Klingon Commander Kruge, but he pulled off a pretty ruthless Klingon. From his first scene when he blows up his lover Valkris for knowing too much, to his last where he knows he is going to die and is determined to take Kirk with him, Kruge makes for a pretty nasty baddie. He disintegrates his gunner after his "lucky shot" destroys the Starship Grissom and doesn't bat an eye when he discovers he's killed Kirk's son. He only shows dismay when most of his crew has been killed when the Enterprise self-destructs, and that's only because he's ashamed Kirk was more cunning than him. Plus, the Klingons as they are shown in this film laid the blueprints for all the Klingons on to come. The Klingon Bird of Prey, which still looks pretty formidable, was still in use 100 years later, as were the uniforms. The Klingons reverence for honor and their thirst for power were firmly established here. Every Klingon seen in subsequent films and countless episodes of the spin-off shows all followed the model laid out here. Not to mention the Klingon language, which has become its own cultural phenomenon, quoted in everything from "Frasier" to "Chuck", got its origins here. Sure, the first film had Klingons uttering the words "Fire" and "Tactical" in their native language. But here, linguist Marc Okrand developed a language that has since been used to translate Shakespeare!