1. f4
The Bird's opening was popularized by the English player Henry E. Bird towards the end of the 19th century. While not enjoying the same level of success as, say, King's Gambit or Queen's Gambit, it can be an effective start against one's opponent.
1.f4 e5
2.fxe5 d6
This is black's aggressive response to 1.f4, and can usually be an effective one. If black isn't quite as aggressive, white can hold a good monopoly on e5 and the kingside rook can get out pretty easily by way of f1f2 then f2 c2.