The Keoni-Hiva Gambit is the Deadliest Gambit around. Clyde Nakamura came up with the Keoni-Hiva Gambit as a mirror image of the Franco-Polish Gambit.
The following account is taken from Chessville;
The story of the Keoni-Hiva Gambit started with the Franco-Polish Gambit (1.e4 e6 2.d4 b5). I had wanted to create a reversed form of the Franco-Polish Gambit from the white side but after the moves 1.e3 e5 2.b4 Bxb4 3.f4, I was surprised that black had 3…Qh4+ 4.g3. I had realized that I had arrived at the same position as in the Franco-Polish Gambit a move too early.
Thus was born the idea for the Keoni-Hiva Gambit. I decided to use the same ideas as in the Franco-Polish Gambit, but I had to leave out the b4 move. The initial moves for the Keoni-Hiva Gambit that I first experimented with were: 1.e3 e5 2.Nc3 Nf6 3.f4 exf4 4.Nf3. It was only after playing many games with this gambit that I realized that there were 2 other starting variations. The Hawaiian names for the 3 main lines of the Keoni-Hiva were provided by Eric Schiller.
Keoni is the Hawaiian nickname of my chess student and Hiva is the mythical place where ancient Polynesians came from. Yes, I do consider the Keoni-Hiva Gambit my most deadliest gambit. It is still a work in progress. There are still much improvements to be made in the various lines.
The kingside attack in the Keoni-Hiva Gambit is very strong. Essentially white sacs 3 pawns for a kingside attack. Being 2 pawns down, white has to play for the win. There is no turning back. If your attack fails then you will lose the endgame. Computer opponents tend to take all 3 of the pawns. Against human opponents you could see more variation in the number of pawns being taken from 1 to 3 pawns taken or even declining the gambit altogether.
The moves for the Keoni-Hiva Gambit is as follows:
Line 1 (Akahi Variation):
1.e3 e5 2.Nc3 Nf6 3.f4 exf4 4.Nf3
Line 2 (Alua Variation):
1.e3 e5 2.Nc3 Nc6 3.f4 exf4 4.Nf3
Line 3 (Ekolu Variation):
1.e3 e5 2.Nc3 d5 3.f4 exf4 4.Nf3
1.e3 d5 2.Nc3 Nf6 3.a3 e5 4.f4 exf4 5.Nf3
Play through the variations and a couple of sample games to get a feel for the Keoni-Hiva Gambit.