The Caro-Kann is a solid defensive opening for Black but it does have scope for imaginative maneuvering from both sides. The Alekhine is sharp by it's very nature. Black is almost taunting White with his Knight as he draws the central White pawns forward. It's a natural breeding ground for tactical shots.
The Nimzowitsch Defense is a less tried opening that Black can call on. It also contains a gambit.
The Alekhine Gambit is the first of three in the Caro-Kann Defense. Alekhine had a good record with this ploy. Black has several possible responses in the position. The two main replies boil down to accepting with 5...Qxd4 or declining with 5...Nxe4.
Both of these moves are quite successful for Black. 5...Qxe4 has a 47% win rate for Black with White winning just 30% of the time. It's clear that White cannot prove he has adequate compensation for his d-pawn.
5...Nxe4 is even better for Black with a 50% success rate after this move. White wins just 1 in 4 with a further 1 in 4 ending in a draw. By declining the gambit Black does not allow White to get a lead in development.
The Rasa-Sturdier Gambit comes about when you go for a Blackmar-Diemer set-up against the Caro-Kann. The main characteristic of this gambit against the Caro-Kann is the absence of White's Queenside play.
In a regular Blackmar-Diemer you would see the light square Bishop regularly on c4 or b5. Not in the Rasa-Sturdier as the Black pawns on c6 and d5 rule that out.
You will trying to castle Queenside and launching the Kingside at Black. Nc3 and Bf4 will be played quickly. The Queen will go to d2 or f3 and you will then castle. Pawn storms primarily on the g and h-files will set the attack in motion.
The Godley Gambit is a great way to reintroduce some imbalances back into the game if White opts for the Exchange Variation. White may want to suck the life out of the game with 3.exd5. 3...Nf6 invites White to take another pawn where you would get a lead in development.
After 4.dxc6 Nxc6 5.Nf3 Bg4 6.c3, Black has three minor pieces developed to White's one. Even though White seems to have a fearsome Queenside pawn chain led by the proud d4-pawn he will not get it all his own way.
Black can launch a minority attack on the Queenside. When his two pawns disappear, White's pawn chain starting on a2, b2, c3 and d4 will be greatly weakened.
You can sacrifice the d-pawn with 7.Nxe5. After 7...Bxe2 you can still hold this pawn with 8.Kxe2. This moves carries all of the obvious risks that come with a King wandering around the center with an enemy Queen and Rooks still on.
The Queen usually takes leaving the d-pawn hanging. What do you get for this gift? You should end up with better minor pieces in the Bishop & Knight vs Bishop & Knight endgame. Black's b6-Knight is poorly placed and his dark square Bishop is still waiting to be released. Your pieces can get better squares quicker.
Is this enough to win? Maybe if your technical prowess is top notch. If not you may struggle to justify this slight edge as valid compensation for the pawn.
Richard Spielmann was another who contributed to the fireworks in the Alekhine Defense. He threw in a developing move with 2.Nc3 and only after 2...d5 did he push the e-pawn. The surprise comes after the Black Knight retreats to d7. Spielmann's idea is 4.e6?!
The point of the sacrifice is clear. By forking the Knight and f7-pawn, White has forced the immediate 4.fxe6. Black's Kingside has been dealt a fearsome blow with f7 ripped open. White also finds himself with the lovely e5 outpost beckoning his King's Knight. Not a bad deal for a pawn.
The weak e8-h5 diagonal and the e5 outpost will feature heavily as White launches swift attacks in a bid to capitalize on his initiative. If Black is tempted to play ...g6 to prep the fianchetto and lock the White Queen out of h5 he is in for a nasty shock. You have h4! threatening h5 to tear the Kingside asunder waiting in the wings. The Black King would be in hot water in short order.
Gambit Chess Opening: John Tracy Gambit - 1.Nf3 Nf6 2.e4
You can try 2.e4?! to maybe get a lead in development. The point after your pawn is devoured is you can win tempi off the advanced Knight and take a lead in development.
If you face this with Black don't be shy. Accept the pawn with 2...Nxe4. It's perfectly safe and you can fight off any initiative White generates with good, solid play. Simple no nonsense development, castle your King and you should be good.
You could also turn down the offer if you don't feel like punishing White's dubious second move. 2...d5, 2...d6, 2...e5 and 2...e6 have all been tried with reasonable success but none as good as 2...Nxe4.
The Colorado Gambit is a great way to shake White up when he plays 1.e4 against you. You can avoid passive positions arising from sterile interpretations of the Ruy Lopez or the Sicilian.
I say this not because I think that these two openings are sterile, I don't. Both of them actually contain lots of potential for Black to reach stimulating scenarios. You can only get the most out of these openings through a lot of study. You must learn the deep conceptual ideas behind these openings to avoid tripping up in their sharp variations.
The Colorado after 1.e4 Nc6 2.Nf3 f5 may have a less challenging learning curve. It gives you the chance to gain a big center as Black against 1.e4. This alone is remarkable. Then there are all those juicy traps you can spring on White.
The Caro-Kann, Alekhine and Nimzowitsch certainly provide much opportunity for interesting positions. Even if these gambits do not form part of your core opening repertoire it's still advantageous to play them now and then.
Not only are they fun to play but playing these imbalanced games can teach you how to play with pawn minorities/majorities or playing after an exchange sacrifice perhaps.