Ranking gambits

Here, i give a score out of 5 for various gambits; in terms of how effective and interesting they are. "Gambits" that do not actually give up material like the queens gambit, or gambits that are just a cheap trap (Blackburne-Shilling) are left out. 

5 out of 5; the best, most respected gambits. A clear plan and compensation for the lost material. 

-Benko Gambit

-Evans Gambit

-Ruy Lopez; Marshall attack

-Sicilain Najdorf; poisoned Pawn variation

-Two knights defense variations with 4. Ng5 d5!

-Kings Gambit

4 out of 5; Somewhat risky but but sound if you know what you're doing. 

-Goring Gambit

-Kings Gambit Declined; Falkbeer counter gambit

-Queens gambit declined; Albin countergambit

-French Defense Winawer; poisoned pawn variation

-Froms Gambit

-Muzio Gambit

-Fried Liver attack 

3 out of 5; rather dubious but may work as a surprise. 

-Grob gambit

-Smith-Morra gambit

-Sicilian; Wing gambit

-Caro Kann defense; Rasa-Studler Gambit 

-Double Muzio gambit

-Staunton Gambit

-Traxler Gambit

-Bryntse Gambit (Gambits the queen!) 

2 out of 5; with corrent play the opposing player gains an advantage. These gambits can be considered refuted.

-Latvian Gambit

-Elephant gambit

-Bishops opening; Calabrese countergambit

-Kings gambit; Bryant countergambit

-Englund Gambit

1 out of 5; bad gambits that are probably worse than Carlsens "Bong Cloud" opening

-Reversed grob/borg defense

-Haloween gambit

-Jerome gambit

-Smith-Morra gambit with 4. Bc4

-Anit-Reti gambit

-Omega gambit

-Duras Gambit

0 out of 5; Damiano gambit. 

where do you rank Philidor Counter Gambit ?    Here are several videos explaining that gambit by NM James R West   https://www.chess.com/blog/JimWest?keyword=philidor

2 out of 5. It's been analysed as advantage white with correct play. Both 4. Nc3 or 4. Bc4 lead to advantage White.

All these "kings gambit wanabee" gambits for black don't seem to work very well, same with the Latvian etc. 😉

Nice list! The only one I don’t like is the KG at 5/5 cause modern theory has practically refuted it with exf4 Nf3 Nf6!

Budapest Gambit: 4

oh, and don't forget to rank this gambit: (I'd rank it 3-4)

KG 5/5? Bwahaha

I suggest the Irish Gambit for 0/5

No Icelandic or Danish gambit  ?

Scotch gambit/Max Lange.

No Scotch? Sad.

Seems tough to compare Black and White gambits on the same terms.  Some of the White gambits you give -- the King's and Evans, for instance -- are probably good for a draw, but with precise play black can equalize and white has forfieted the advantage.  Maybe we can call that "sound," in a certain sense, but the result is still that grandmasters don't play them in serious games.

Whereas, if you could get the same thing with a black gambit -- equality -- then you'd absolutely call it sound.

The OP has a few missing and a few misplaced.

Kings Gambit - 3 at best

Lolli Gambit - 1 (It is an even worse version of the Kings gambit, After 1.e4 e5 2.f4?! exf4 3.Nf3 g5 4.Bc4? (Lower it to a 2 now) g4 5.Bxf7+ (Now a 1))

Queen's Gambit - 5 (and yes, some lines are a true gambit!)

Relfson Gambit - 2 (1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bb5)

Rubinstein Gambit - 5 (1.e4 e5 2.Nf3 Nc6 3.Nc3 Nf6 4.Bb5 Nd4)

Marshall Gambit - 4 (In the Triangle Defense - 4.e4)

Scandinavian Gambit - 4 (1.e4 d5 2.exd5 Nf6 3.c4 c6 - more sound than the Icelandic - so much so that White should decline it by transposing to the Panov-Botvinnik Attack)

Danish Gambit - 4 (OK, but Black equalizes completely after 1.e4 e5 2.d4 exd4 3.c3 dxc3 4.Bc4 cxb2 5.Bxb2 d5! 6.Bxd5 Nf6! 7.Bxf7+ Kxf7 8.Qxd8 Bb4+ 9.Qd2 Bxd2+ 10.Nxd2 and it is 0.00)

The main way factor is how hard it is for the opponent to gain equality/advantage over them. For example the Evans gambit is harder to gain equality against than the Smith-Morra etc. People here are saying that the KIngs gambit isn't great, but in a practical game it creates wild tactical complaications where it's not so easy to find the right moves. Wheras against the Latvian, just follow a bit of basic opening theory and you already have an advantage.

Ofc finding the right moves against Gambits isn't a problem for computers but us humans are always gonna make blunders  

You have to add the Nakhmanson Gambit, here's a video on it: https://www.youtube.com/watch?v=2n8TAR69EyY 

Kin gs Gambit should be rated about "2" as The defense 1. e4  e5  2. f4  exf4  3. Nf3  Nf6 is close to winning for Black.  However White can try  1. e4  e5  2. f4  exf4  3. Bc4.  

Here is a gambit not mentioned.  I used it to beat a GM at a US Open. 

I call it the Goring Gambit 2 pawn Sac.

My opinions: Cochrane gambit is almost sound. There are gambits for both colors in the Tarrasch QGD that are also almost sound. Schliemann's soundness depends on the opponents memory. I'd say it is sound for 99% of human players. White has a piece countergambit in Schliemann that is has a thin line that refutes it but was sure fun to play before computers found it! In the classical defense to Ruy, the 5 d4 line has [if I recall correctly] a gambit subline that always seemed sound to me.

Rice Gambit.