Acetylene gives a nice boom. My friends and I used to fill balloons with it by putting a bit of calcium carbide lamp powder and water in a coke bottle and the balloon over the top. Tie it off when filled and drop it over a candle. Our mom’s would come out yelling when we did it in our back yards.
Actually, OP could scare away gulls pretty cheaply using this same method!
Wow, I never actually know what the old Calcium Carbide and water made !!
Just had a google and yeah ACETYLENE . . . cool !!
We had a couple of the old lamps under the house (or rather dad did) when we were kids, never used them, but often put the CC bits into a bottle, some water, seal it up and run !!
Not as dramatic as lighting it up but it would blow the bottles up nicely, ha ha.
Interestingly, CC was used up in north Queensland (where we grew up) for Banana plantations.
The gas would ripen the fruit somehow !!
Thinking back, it's amazing we survived all the things we got up to, making explosive devices from ammo (.303 and other, shotgun shells, cordite, primers (filed open very carefully), mates on farms with detonators and home made gelignite.
Town would have heard some nice big BOOMS sometimes ?
I can remember making .303 cartridge 'rockets', older stick cordite shells with a stick or two out the open primer end, put into slightly oversize pipe, light it up.
They would go off like a WWII V2 rocket through the air, white flume of smoke behind it !!
Did many, until one day one went off in the pipe (cartridge exploded) right next to my ear . . . yes I was holding it on my shoulder like a rocket launcher.
My ears were ringing for hours, and really lucky that pipe held out.
Now THAT would put the wind up the seagulls, a couple of V2's going their way, arm the drone
@Philgib 
