Modern benoni is a very tactical opening. The Benko is also a good opening (but not with e6 that you showed) and the slav is a good opening as well.
Strong tactical response to d4?

The KID can be razor-sharp, but someone who plays d4 at a decent level is likely to know a good response + theory. I gave up the Benoni because I realized that I sucked at playing those positions. Might take it back up though since I've improved a lot since I played it.
The Budapest Gambit?

What about the blumenfeld agambit?
It can be avoided but you have a series of other lines you could use if they do.

I do play the French and I have been trying out the Dutch stonewall, but I find it difficult to play as Black because his position is quite passive.. However the lines where white doesn't play g3 are fun.
Btw, I forgot to give a bit of context, this preperation is for a rapid tournament (30/0) in two days time, so I need an opening which I can learn pretty quick!! So that rules out KID/Grunfeld etc... But I want a sharp game, so I have good winning chances, and possibly something that my opponents will not have a prepared response for.

If your goal is to win the best way is to play something you know very well rather than something you just learned.

Are the Englund and Budapest gambits worth looking at? Also I just thought I'd say, my rapid play grade is 1750 (138 ECF) so it's unlikely my opponents are versed in much theory, nor prepared for these Black pet defenses..

Learning a new opening for a tournament in two days is the perfect recipe for a complete disaster. Stick to what you already know for this time.

If your goal is to win the best way is to play something you know very well rather than something you just learned.
I change my repertoire a lot.. particularly against d4.. Most recently, like I've said, I've been trying to Stonewall but it's too passive and positional for my taste

The Budapest gambit has netted a friend of mine (~1600) wins over 2000+ players on 6 separate occasions. That's all I can endorse it with, though, I've never played it.

Are the Englund and Budapest gambits worth looking at? Also I just thought I'd say, my rapid play grade is 1750 (138 ECF) so it's unlikely my opponents are versed in much theory, nor prepared for these Black pet defenses..
When you dont care about, if an opening is sound or not, then I think you should give the Englund and its sidelines (2...d6 and f6) a try. You need to have good tactical skills and then its a great weapon for black in OTB, blitz and bullet, sure not on higher master level, but on a good amateur level (as you play).
If you are interested, we can discuss it, i can give you some theory recommendation about and show some general concepts, not much to learn compared with standard openings.
the budapest is the kind of thing where you can either get a very good position out of the opening, sometimes just winning, if your opponent knows nothing about it, but if they do know what they're doing you may well just end up having to defend a lot.
the opening is certainly not as bad as its reputation though. it's worth looking at moskalenko's book on it if you are interested in it.
when it comes to d4 the only truly sharp openings seem to be the kid and the gruenfeld which are both very theory intensive and hard to understand / play. of course other openings can be super sharp, like the semi slav, but like pfren says that depends on white going for the sharp lines.

first line that came to mind was the dutch but its best to study it first 9 times out of 10 i just play slav lines as its quite easy to do and the knights are very good pieces in it if you want to get at your opponent quickly then benko is a great line opener

One problem is the Budapest is avoidable, as is the Albin Countergambit, and the England Gambit is outright crap.
1.d4 Nf6 2.Nf3, now what?
Compare that to say, the QGD, QGA, Slav, KID, Grunfeld, Queen's Indian, etc, you have 1.d4 d5 2.Nf3 Nf6 3.c4 e6 (or 3...c6 is the Slav or 3...dxc4 is the QGA) or 1.d4 Nf6 2.Nf3 and now 2...e6 3.c4 transposes to the QID or Bogo-Indian or QGD, depending on Black's third move, and 2...g6 3.c4 transposes to the KID or Grunfeld, but in all of those cases, you must also know what to do against the London, Colle (not good against g6 lines), Barry Attack (doesn't work against e6 or d5 lines), Torre, etc.
I can tell you that I often exercise this , either via 1.Nf3 d5 2.d4, 1.Nf3 Nf6 2.c4 g6 3.g3 Bg7 4.Bg2 O-O 5.O-O d6 6.d4, 1.d4 d5 2.Nf3 Nf6 3.c4 intending 3...c6 4.Qc2, 3...dxc4 4.e3, or 3...e6 4.g3 (Catalan), or 1.d4 Nf6 2.Bg5.
So if this event is only a day or two away, play what you know. If you aren't facing GMs, you can win with any opening as Black. I've won many times with the QGD. Simply outplay your opponents.

The tarrasch might be what you're looking for, since it can be played against both 2.c4 and 2.Nf3 (and even against 1.c4 and 1.Nf3 in fact, white's best bet is to allow a trasposition) and leads to active piece play in most lines (expecially in the tame lines you usually encounter at club level). But not for a tournament which is just two days away! You really needs some time to get a feel for the resulting positions, I scored miserably for a while after adding it to my repertoire (now i'm doing very well though).

Yes, the main issue is that in the main line 1.d4 d5 2.c4 e6 3.Nc3 c5 4.cxd5 exd5 5.Nf6 Nc6 6.g3 Nf6 7.Bg2 Be7 8.O-O O-O, 9.dxc5 leads to positions where you need to significantly outclass your opponent to win as black; if white plays passively often the "punishment" is merely that black manages to exchange to isolated pawn with a just marginally better or even dead equal position. I must say that at my level (1875 fide) i never had particular problems over the board in generating winning chances, but i sometimes felt the drawishness of the line when playing online.
9.Bg5 c4 is less of a problem in terms of creating winning chances unless your opponent is really booked to death (which may happen to pfen i guess, but certainly not in amateur practice); as soon as white plays a slightly passive move black queenside majority can set in motion, and black has every hope of playing for a win.

Yeah, I was going to play the Tarrasch, and I bought a Grandmaster Repertoire book on it, but I realised it is so rare for Black to get a typical IQP position (which is what I wanted) that is really wasn't worth learning all the theory to it (which was also a lot more than I thought). I have taken a look at the Englund but it seems Black has to learn quite some theory there and can't even be assured of a good game..
The Budapest Gambit looks a lot better than the Englund gambit, and I think I would feel comfortable in those positions, where you rook lift and get a cheap attack against the king (I play the Colle-Zukertort). Do you have to learn much theory for the Budapest?
I have also looked into the 3...dxc4 line of the Slav, which I have found out is called the Geller Gambit. Is this any good? I think because I have some experience playing this in blitz, it maybe better for me than the Budapest. I really like Black's queenside pawn majority and in many lines he just remains a pawn up. However the lines where white plays a4 before Black plays b5 look annoying. Any opinions on this line?
Yes.... this is yet another patzer looking for the perfect (sharp, attacking, non-theoretical) response to d4......
I don't mind if the opening is slightly dubious, but I want to hear some suggestions for good, tactical, and possibly unfashionable (more likely the opponent won't know theory) lines, that deviate from the mainline early (less chance of the opponent going off the mainline before I do). If anyone knows any good SOS's (Secrets of Opening Suprises) against d4 in general, it would be interesting to hear them.
The reason for looking for some unsound opening line is that I feel the Stonewall is too passive with too few tactics for a rapid game..
So some lines I was looking at were a sideline in the Benko..
And I was also looking at this Slav sideline which I genuinely know nothing about, but have toyed around with in blitz
Does anyone have any opinions on these variations or any other interesting, neglected, and possibly dubious openings in response to d4 they'd like to mention?