The Max Lange Gambit
1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. 0-0 Nf6 5. d4!?
Bd4 6. Nxd4 Nxd4 7. f4 d6 8. fxe5 dxe5 9. Bg5

Here are some theoretical games, with a theory "game" showing our preferred lines. Max Lange successfully played this gambit in the mid-1800s. You also need to know the Max Lange Attack, in case your opponent plays 5. exd4.