We used to use fishing nets to catch bees; I'd imagine jars work just as well though.
Usually it's just a case of me trying to kill an especially annoying mayfly but not quite succeeding, just injuring it, so it limps around for a bit and tries to fly but can't get very far. I hate insects and I'm sorry if that's a crime =/
The most evil thing I did was god knows how long ago, I must have been about eight. My best friend found my mum's lighter (my parents were still smoking back then) and we took it out into the garden and tried to set fire to a slug. It didn't so much burn as... melt.
As kids my brothers used to have this obsession with trying to bomb live jellyfish with gigantic rocks; something I was never tempted to do unless they were washed up. Sends bits of jelly flying for metres if you hit it hard enough.
Oh and one other thing but this wasn't me, it was a friend of mine. We found this crab washed up on the beach, upturned and not moving, so just out of sheer curiosity my friend pulled its shell off and it's heart was still beating

For some reason, I've never tried crabmeat.
Jam it back in, in the dark.