What elements (in terms of setting, technology, events, characters, organizations, themes, etc.) would you consider essential to each of the following genres? What elements might you consider common or likely, but not essential? I'm particularly interested in terms of these genres in roleplaying games, though movies, television, books, etc. are just as relevant (if you think there will even be a difference).
Fantasy
Science Fiction
Cyberpunk
Post-Apocalyptic
Horror