Christopher Plummer
This is not my absolute favorite movie, or the absolute favorite movie of any of my friends, but as a group, it is our collective favorite movie.
One of the many, many things to love about this movie is Christopher Plummer. His lines are as silly as anyone else's, but he manages to imbue them with real dignity. I saw a public screening in Boston last year (it was my 6th or 7th time viewing the movie). Throughout the screening people were laughing and making fun of the movie (as one should). It got to the scene where Christopher Plummer first appears, giving a monologue in hologram form. Soon, all the noise in the theater died down, and audience was silent for the entire monologue.
Some reviewers remark that Plummer looks embarrassed to be in this movie. I've never seen that in his performance, and I recall reading a quote by him where, having been asked why he took a role like Starcrash, his response was "How could I possibly turn down the chance to play the Emperor of the Universe?" It's great that he not only approached this with the proper sense of fun but also brought his A-game to it.
(also the director Luigi Cozzi clearly gave him the best costume in the movie)