The Flagship Trap is a line in the Ponziani Opening where white sacrifices a queen in exchange for a deadly attack.
The Ponziani Opening starts out with the moves:
1. e4 e5
2. Nf3 Nc6
The Flagship Trap comes into play after
4. d4 Nxe4
5. d5 Ne7
Black has a cramped position and white is looking to attack. White will look to get the light square bishop involved into the action and dominate the game with minor pieces. White can even sacrifice the queen on d1 in exchange for a tempo advantage in the minor piece attack.
To watch an overview of the Flagship Trap you can check out the video below.