This is the position from Stubbs vs. Helbig in a recent Division One match:

White is beginning to take some control, utilising extra space and time; and is threatening to really tighten the screw and maybe land a piece on b6, supported by pawn c4-c5. This is just one possible plan, but it would also free the bad bishop on d3. However, Paul wanted that bishop to stay bad, and so played the deep queen sacrifice:
…Bxc5!
He gives up the queen for a rook and bishop after Rxb8 Rxb8 Black has three relatively active pieces which stand a good chance of stopping the queen rampaging – and the potential of co-ordinating to pressurise the king or get a pawn moving down the board.
Would you have thought of this move? It’s important to at least consider them. After a good 4-5 seconds thought, Stockfish comes to the same conclusion as Paul and gives up the queen also! Here are the lines:

In the game there followed Qc3 Bd4 Qxa5 c5:

Without the a-pawn White would have no real way to make progress, and still has the weak bishop on d3 -which Black goes for now. Surprisingly, White simply gives the bishop up straight away rather than try to wriggle to worse and worse squares, and gets the pawn moving: Qa7 Rb3, a5! Rxd3, a6 White had worked out that the Black rook would have to sacrifice itself too for the pawn, but hadn’t counted on the bishops being so strong afterwards! Bxc4, Qb8+ Kg7, a7 and Black must give up the rook:

After a8=Q Rxa8, Qxa8 the bishops and the extra pawn provide Black with enough stability and potential counterplay to distract the queen from doing any damage. White tried the best plan to disrupt the pawns and open more lines for the queen, but had to settle for a perpetual check and a draw was agreed.
That’s some defence!
The rest of the game went Bd3, g4 g5, Qd8 h6, h4 gxh4, g5 hxg5, Qxg5+ Kf8, Qd8+ Kg7, Qg5+ Kf8, Qd8+ etc.
Always consider the defensive sacrifice – it may just be the best way forward.
Mike is co-editor of the Bristol Chess Times and plays regular league and tournament chess