The Queen and Knight combo is very effective in hunting the king. Here's one example of how they can work together to deliver mate.
The position occurred in the following game:
1.d4 Nf6 2. e3 d5 3. Bd3 c6 4. Nd2 Bg4 5. Ngf3 e6 6. c3 Nbd7 7. Qc2 Bd6 8. h3 Bh5 9. O-O Qc7 10. e4 dxe4 [Black hasn't castled yet so the pawn break e4 makes sense]
11.Nxe4?! Bxf3 [Nxe4 allows Black to break White's kingside]
12.Nxd6+ Qxd6 13. gxf3 O-O-O 14. Be3 e5 15. Bf5 g6 16. Bxd7+ Nxd7 17. dxe5 Nxe5 18. Bxa7?? [A blunder which Black takes advantage of]
18....Nxf3+ 19. Kg2 Nh4+ 20. Kg1 Nf3+ 21. Kg2 Qf4 22. Be3 [Now Black has a forced mate]
22....Nh4+ 23. Kg1 Qf3 { Black wins on time. } 0-1
My opponent was not a good sport, didn't resign and let his time run.