The Tennison Gambit is an aggressive line against the Scandinavian defense that starts with the moves:
1. e4 d5
Black is almost always going to capture the pawn on e4 and white should respond with Ng5. This puts black in an interesting position. If black tries to hold onto the pawn advantage there are many lines where black will forfeit his position or even the lead in material.
If black does not hold onto the material, white can recapture and have a very good development in the game. With perfect play, black will come out ahead, so be careful trying to play this opening against really good opponents. For someone that is unfamiliar with this as black it can be very difficult to play correctly.
Make sure you check out the video below to learn more about all the variations.