sharpest reply against d4

The issue with the subject of sharpest openings is that the opponent always and esp as white can decide how sharp the game is going to be. a sharp game takes two players that want to get involved in a slugfest.

Taking advantage of passive play is another subject and is relitively easy to do as black or white.

1 d4 is not a passive move, If you want to signal a fight then I'd say KID as this is used by plenty of players that like to play tactically

I happen to really like this 3 video series from GM Perelsheyn on King's Indian Defense (KID).  May not be the opening you choose to play, but you will learn quite a bit from this GM.  I hope that helps.

http://www.chess.com/video/player/the-kings-indian-defense-beating-the-fianchetto-systempart-1

To the OP: Yes it is the Modern Benoni! At least imho

It tends to get sharp and complicated, fits well with an overall 1...c5 repertoire and it's generally fun. As has been pointed out you need a suitable answer if White chickens out and foregoes d4-d5. I suggest exploring along the gambit line 1.d4 Nf6 2.c4 c5 3.Nf3 cxd4 4.Nxd4 e5.

I have written a bit about the MB in my blog, check it out if interested:

http://www.chess.com/blog/Torkil/defending-against-1d4---the-modern-benoni

http://www.chess.com/blog/Torkil/the-modern-benoni-and-your-repertoire

http://www.chess.com/blog/Torkil/mb-reloaded

Hello,

     Openings like 1. d4 d5 2. c4 the Queen's Gambit and 1. e4 e5 2. Nf3 Nc6 3. Bb5 the Ruy Lopez aka "Spanish Torture" dominate the professional chess scene because of the extended initiative White can bring to bear upon Black. Some book lines reach well beyond 25 moves in each of these openings.  That's an awful lot of pressure for an awful lot of time so it's only natural that Black, especially at the lower levels of tournament play, would seek more satisfactory answers . . . . 

     "Sharp openings for Black" mean immediate counter-play.  In the case of 1. d4 by White (the subject of this forum) then we're talking about . . . .

               A.  the Budapest Gambit  which follows 1. d4 Nf6 2. c4 e5?! where after 3. dxe5 either Ng4 or Ne4 can lead to very sharp play.

               B.  Albin's Gambit is probably the sharpest.  1. d4 d5 2. c4 e5?! where the usual follow-up is 3. dxe5 d4 and again ultra-sharp play ensues.

               C.  the Baltic Opening follows 1. d4 d5 2. c4 Bf5?! aiming to solve the problem child of the Queen's Gambit (development of the Queen's Bishop by Black) immediately.

               D.  When White doesn't vigorously continue his attack upon the center with 2. c4 then 2. ... Bf5 often gives him a great deal of initiative against say 1) the Colle System after White's 2. Nf3 or 2) the Veresov Attack after 2. Nc3 by White or 3) the Stonewall Attack after White's 2. e3. 

              E.  Perhaps the combination of most solid approach for Black after 1. d4 d5 2. c4 and sharpest counter response which is well respected even among most professionals is the Tchigorin (or Chigorin)Defense which follows after 2. ... Nc6 by Black. 

              F.  The Dutch Defense after 1. d4 f5 is almost as provocative as the Albin Counter Gambit especially if Black decides to castle kingside.

              G.  Returning to much more complicated waters are the Benko (Volga) Gambit and also the Benoni Counter Gambit which are considered so much more respectable that they're encountered fairly often in the armories of numerous professional players . . . both can be extremely sharp but they are also plotted out many moves deep by these professional players.  Less sharp openings can become extraordinarily tactical say, by move eight in the hands of professionals (King's Indian Defense; Queen's Indian Defense; Bogo-Indian Defense; Nimzo-Indian Defense to name a few . . . but they do not fit in with the spirit of the forum question because "Sharp" for Black means offering immediate counter-play.

     Most importantly for non-professionals playing in clubs or in class tournaments . . . these ten openings mentioned earlier are a lot of fun and winnable for Black against all but the most circumspect play by White.  Happy Hunting!

With the triangle move order, which I believe is 1. d4 d5 2. c4 e6 3. Nc3 c6, I would still do cxd5, they get to choose between the Slav Exchange or the Queen's Gambit Exchange. Again, not what the OP wants

of the triangle strength in pyramids

It's impossible to guarantee sharp positions 100% of the time. But IMO the Triangle gives Black the best chances for a sharp game. The point is that taking on d5 there is a completely harmless line, as Black can freely develop his LSB (therefore it's not all that common)

In the KID, White also has "spoiler" lines like the Fianchetto, the Averbakh to some degree and especially the Exchange, which in my experience are far more common at club level than the "spoiler" lines in the Triangle (although my experience in the KID is greater than that in the Triangle so I could well be wrong)

EDIT : You can, of course, avoid the Exchange with 6...Na6 or 6...Nbd7 but neither are nearly as sharp as the main line Mar Del Plata

Benoni games do tend to get wild, just look at this game here:

I think the reason why the "spoiler" lines would be more common in the KID is that 2...Nf6 is more common than 2...d5. There is nothing I can do to prevent the KID setup if black is determined to get to it when I play 1. d4, and judging from my losses, the tactics shift towards the center instead of against my kingside.

Dutch is nice

I like the responses given, one of my favorite chess strategy's is to keep it ultra positional until around move 15- 20 and then start creating wild play

1 d4 Nf6 2 c4 Ng4

is called the British Indian.

Problem is with learning these lines, your opponent then goes on to play the London system or something as equally dull. 

For people recommending the budapest, there's 2 ways to play it. The sound way's are ok for black imo but nearly impossible to ever win unless your opponent blunders, otherwise you can go for something like the black jet (g5) or the crazy rook plan. But sadly these lines are pretty refuted...

you could try the czech benoni

I believe the sharpest reply to d4 is something that opens up the position.

you could try the albin counter gambit

1.e4 is best by test

because it leads to better positions for white.  anyone who tries to play chess with 1.d4 is probably just scared of tactical positions.  ha ha ha

The Modern Benoni is perhaps the best way to consistently get sharp positions. Against the Colle and London, you can aim for reversed Catalan and Reti positions, sometimes sacrificing the c-pawn for decent compensation. I don't fully believe in the Modern Benoni, but it is very interesting and you will probably get sharper positions than the Benko.

The Semi-Slav has a lot of sharp postions as well and it has a better theoretical reputation. The problem is that White has some quieter lines that are difficult to avoid if he is not in the mood for a fight. (The Slow Slav with 4.e3 and the Exchange Slav come to mind.) Ultimately, I think this is a reality players should accept as Black, rather than to compromise quality in most normal circumstances.

Another possibility is the Noteboom variation, which can be played through the Triangle move order (1.d4 d5 2.c4 e6 3.Nc3 c6), avoiding the Exchange Slav and a few other anti-Slavs. If White exchanges, Black gets an improved Exchange QGD; however, White has the interesting option of the Marshall Gambit 4.e4!? where Black has to be very accurate to survive. This can be very sharp, but it is a bit risky.

I dare you to say this about the Botvinnik Semi-Slav or Anti-Moscow Gambit with a straight face. :)

Other than gambits, sound and sharp openings against 1.d4 will always include Grunfeld, King's Indian, and the Dutch Defense. Of course these are also the same openings that get repeated beatings at the highest levels but thats the price to pay, being aggressive with the black pieces.

Huh?  The KID and Grunfeld are still alive and well...not all top GM's are pansies!  

These threads always seem to result mostly in people giving their favourite openings, rather thn what OP asked for.

I think clearly the semi-slav, with dxc4 against Bg5 is the sharpest position in d4, probably in all of chess.

The gruenfeld is also very very sharp in many variations.