The Budapest Gambit (or Budapest Defence) is a chess opening that begins with the moves:
1. d4 Nf6
2. c4 e5
Despite an early debut in 1896, the Budapest Gambit received attention from leading players only after a win as Black by Grandmaster Milan Vidmar over Akiba Rubinstein in 1918. It enjoyed a rise in popularity in the early 1920s, but nowadays is rarely played at the top level. It experiences a lower percentage of draws than other main lines, but also a lower overall performance for Black.
It worked very well for me in one of my lichess games.
Black sacrifices his pawn on e5 but then moves the knight to g4 threatening to recapture it. White brings more and more pieces to defend the pawn and Black delivers check on b4 and then attacks the pawn with the queen. White attacks the bishop with the pawn on a3 but Black ignores him and finally takes the e5 pawn. White needs to be careful because capturing the bishop falls into mate in 1 on d3!