Whenever my opponent plays 1.d4 I'm thinking: 'oh god not again..'

My problem with 1.d4 is that I find it very boring. Do any of you guys know a sharp opening, preferably a gambit, for black against 1.d4. Thanks in advance!

Old Benoni Gambit leads to a sharp game alot of times.  1.d4 c5?! is one of my favorite gambits against 1.d4.
http://www.csm.astate.edu/~wpaulsen/chess/chess.htm?000649

http://www.chessgames.com/perl/chessopening?eco=A43

Honestly, I pretty much play everything 1. d4 and 1. e4 ... just bounce around for the sake of learning. 

I'd really suggest you take a look at some mainline semi-slav and other super-positional lines ... they're solid, they're sound (in case you actually want to become a better player), and they'll open up a level of understanding of chess that you simply can't get from tactical bloodbaths.

If all that sounds boring, try the Budapest :P.

Kings Indian Defense is pretty good stuff too...

the budapest gambit leads to sharp play i find. 1.d4 Nf6 2.c4 e5

KID and grunfeld are two of the sharpest lines against d4

Play the semi-slav. The botvinnik and meran lines are very tactical.

I like the Old Benoni. It leads to a lively game.

Try the Nimzo indian or the king's indian. They're not very heavy on the defensive.

King Indian Defense assures you of no yawns. =)

 But if you play the King's Indian practically all the time (like I do) don't you start to get bored of it?

Try the Leningrad Dutch, like the KID but with a pawn on f5.

Well, try the King's Indian and the Volga (Benko) Gambit.

The Meran System is also nice.

The Noteboom is one of the few responses to 1.d4 that allows black to fight for the full point from the outset.  Experienced queen's pawn players will usually avoid it but the less experienced will walk straight into the meat grinder.  It's sharp, complex and hugs the line between respectable and insane which means that it's also very, very fun to play. 

I don't know if you're familiar with the Benko Gambit but for those that are I'll just say this -- if you think the a/b files give black good attacking chances queenside, just wait until you play the Noteboom where the a/b files turn into  Hell's Highway.  You'll never look at the a7 and b7 pawns the same again....I'm gettin' misty just thinkin' about it.

1 d4 d5 2 c4 e6 3 Nc3 c6 4 Nf3 dxc4!?

 But trying to get a noteboom allow the marshall gambit, which scores badly for black.

i always play KID...

The original poster wanted a sharp opening that wasn't boring.  I'm pretty sure the theoretical debate that goes on at the 2700 level doesn't mean much to him or he wouldn't have requested a gambiteering response to 1.d4.  It sounded to me like he was more interested in playing fighting chess that wouldn't put him to sleep.  The Noteboom and Marshall Gambit both qualify in that regard.  The Marshall Gambit is a sign that white didn't leave his balls at home.  Statistics be damned, it's full-point fighting chess.

Having said that, I'm not sure I agree with you that the Marshall is bad for black -- there have been many developments in recent years and it seems that the Qxg2 line is now black's best try.  You can read about it here:

http://www.newinchess.com/Archives/PDFs/YB84_SL61.pdf

 But, just remember... us new players have a limited knowledge and comfort in only a few openings.  I play d4 on white, and siclillian on black... I've learned hard from continually meeting up with the d4 pawn in the center.  Automatically, puts me on defense.. I haven't had a chance to read what others have posted here, but that is my input.

ALBIN COUNTERGAMBIT!!!!

Can Somebody give me the latest theory on Marshall for the line 1.d4 d5 2.c4 e6 3. Nc3 c6 4.e4 dxe4 5.Nxe4 Bb4+ 5.Bd2 Qxd4 6.BxBb4 QxNe4+ 7.Be2 Na6 8. Ba5(Any improvements here?) Bd7 9.Nf3 Nf6 10.Qd6 Qf5 11.Ne5 Qxf2+ 12. Kx Q Ne4+ 13. Kf3 NxQ 14. Rhd1 Ke7 15.c5 Nxc5 16.Bb4 b6 17.Rac1

Theoretically sound, sharp, openings against d4 include:

Modern Benoni

Benko Gambit (My personal favorite)

King's Indian

Grunfeld

Dutch

Choose one of these and you'll be happy.