The Halloween Gambit
This video highlights some variations to be aware of in the aggressive Halloween Gambit of the Four Knight's Opening (Müller-Schulze Gambit or Leipzig Gambit), where white sacrifices a knight early in the game for a single central black pawn, a pawn storm in the center, and a lead in development. The Halloween Gambit is likely not too scary an opening for the black player who is aware of lines where the material is given back favorably in exchange for development, or for the black player who knows how to meet the complex variations where the material plus is maintained. In short, the Halloween Gambit is likely not going to be played on a serious level due to it not being sound, but it certainly has its practical chances in a faster time control game, or even against an unsuspecting opponent. Have some fun with it!