My impression of the word "gambit" is the sacrifice of a pawn or several pawns at the opening stage of a chess game. However, based on the definition on Wikipedia, a gambit (from ancient Italian gambetto, meaning "to trip") is a chess opening in which a player, more often White, sacrifices material, usually a pawn, with the hope of achieving a resulting advantageous position.
The phrase "usually a pawn" seems to imply that a gambit could be a sacrifice of other pieces. Am wondering what are examples of gambits that sacrifice a knight, or a bishop, or a rook, or even the queen, or a combination of these pieces?
I am not talking about blunders at the opening stage that cause loss of material. I am asking about openings that stand the test of time where one side willfully sacrifices some material other than pawns to earn some advantage.
A related question: What is the "biggest" gambit that is still being played at the master's or above level? That is, a gambit that white sacrifices a combination of biggest value of pieces and yet obtained enough advantage development and/or space; at the same time, the game is somewhat acceptable for black as well.