My favorites are the boom hissssssss and whoooosh.
Having cargo door seals blow out is a blast! The fun is offset by the stink that follows. Oh yeah, I did find out that the FO didn't pack a spare pair of tighty whities!
The poster above is dead on about the engine containers and empty sealed barrels.
If you hear other booms or pops you may want to land at the nearest suitable airport. Shifting loads have and do kill. Miami International still has some scars from a DC-8 crashing after a load shift.