I know this thread is a few months old but I'm forever trying to find out where the loud noises are in shows before I go. So this is a very useful resource!
I am as nervy as a nun in a strip club and I jump ALL THE TIME! The ones I have burned into my brain (some spoilers):
Cats:
- Macavity appearing in a bang at the end of the song about him and kidnapping (catnapping?) Old Deuteronomy.
Our Country's Good:
- Captain Phillip shoots at a kangaroo in an early scene - the line is something like "You will have to organise the hanging yourself, and get someone to fill that hideous office". Excellent fun when the "kangaroo" is somewhere in the audience and the gun gets pointed directly at you
Les Mis:
- When Valjean lets Javert go at the barricade and then fires his gun into the air (I think I weed myself a little bit the first time I saw this... it's a blank rather than a sound effect and it is SO LOUD)
- Gavroche getting shot (the shots are spread out and you never expect the last one... EVER)
War Horse:
-One of the captains is testing Joey's ability to withstand loud noises fairly near the beginning, and he fires his pistol into the air twice
- The German soldier shooting the dying white mare in the second half
- The same soldier (I think) shooting at the little French girl a few moments later
- The fricking tank, at least when it first enters, the music gets drum-heavy and very loud too.
The Light Princess:
- The prologue - "A Sealand spy shot Althea's brother, Prince Alexander, dead." *BLAM*
- Digby shooting at Althea - luckily this is massively signposted with Digby raising the gun and Althea saying "Fly bird!"
- The dragon attack near the end of the show, the screech is so powerful, I think I have tinnitus from it
Blood Brothers:
- When Mrs Johnstone sees Mrs Lyons putting the shoes on the table, she shouts "WHAT ARE YOU DOING?"
- The drumbeats on the Narrator's warning to Mrs Johnstone, "But a debt is a debt... and MUST. BE. PAID."
- Sammy during the robbery in the second half - the two shots comes after a line that's something like "This isn't a toy! Listen... listen -"
- Obviously the finale - "I could have been him - I could have been-" *GUNFIRE GALORE*
Mary Stuart (the one that was just at the Duke of York's):
- Horrible grinding noise as Mary is released from prison to go out in the fields
- Again at the end after Mary is executed
Wicked:
- The dragon head thing roaring and clanking at the beginning
- When the professor brings the lion cub on in a cage, and Elphaba's annoyance makes the cage door open with a bang.
Mary Poppins:
- In the kitchen scene, something explodes and sends steam everywhere - can't for the life of me remember what actually happens in that scene even though I've seen it twice! Robertson Ay is involved somehow I think.
Closer at the Donmar:
- The beginning of the club scene, which opens the second half - music came blaring on out of nowhere, I think we all jumped.
Couple of other famous ones:
Assassins - basically the whole show, I won't go near it because I will probably throw up from the stress
Children of the Sun (at least, the most recent National Theatre production) ended with an enormous explosion and apparently set the fire alarms off the first time.