1. Any Merlin but especially 4 x Merlin at high power (4 x Griffon was never quite the same):
2. 4 x Olympus, especially if reheated (sorely missed):
3. The Blue Note:
4. The Napier Sabre, as captured on one awesome recording:
5. Non-military but 4 x RB211-524 idling after start in the BA 747 that's taking you home after too long away.