Called the Zürich Gambit, this very unsound and dubious gambit gambits the g4 pawn to 2...Bxg4. Moving the g-pawn so early weakens White's kingside and is generally not advised.

Black should take with 2...Bxg4 as it is simply a free pawn. 3. Bg2 then usually follows, then Nf3 or h3. Black simply wins a pawn and White doesn't have much compensation except potential surprise value and the semi-open g-file for kingside attacks. However, playing g4 immediately is premature.

Declining the gambit, usually with 2...Nc6 or 2...e6 is principled development and questions White's strange g4 pawn push. White is left with an awkward pawn on g4 still under attack (although potentially they could play 3. Bg2 to insist on gambitting the pawn) and a weakened kingside.

A move that counterattacks in the center and ignores g4 is 2...c5, attacking the center and the d4 pawn. This could be seen as a countergambit, but 3. dxc5?! gives up central control and the g4 pawn is still hanging anyways.

Overall, the Zürich Gambit is an unsound and dubious gambit usually played to surprise the opponent or to exploit the semi-open g-file if Black accepts the gambit.