Jerome Gambit
This gambit is fun, but chances are you might lose. Only try it on lower level players. It requires the sacrifice of not one, but two pieces in exchange for development and castling privileges.
1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. Bxf7+? Kxf7 5. Nxe5+ Nxe5