The smell of spent "caps", as used in cap guns brings back vivid memories for me. We used to buy them on a roll, little dots of gunpowder on pale blue paper.
They were made to fit into a toy gun and you could fire off a whole roll, tearing off the spent ones as you went. We often used to make our own "bangers" using two bolts threaded into each side of one nut, the middle of the nut packed with caps. We would throw them into the air and they would BANG on impact.
And speaking of smells, "Stink Bombs" were always popular. I'm sure they must still be around but, fortunately, I haven't noticed them.
In the days when public transport in the U.K. was actually popular, we would wait for the queue to build up at the bus stand and then, walking innocently past, one of us would stop to tie an imaginary lace while dropping a couple of "stinkies".
Despite the awful smell, no-one would want to give up their place in the queue, so there they all stood, paragons of British stoicism, with handkerchiefs over their faces.
I'm so glad I have a daughter. Girls are much nicer than boys.