Someone told me today of a fly swat that is electrified so that you zap as
soon as you hit the fly.

Yes I was at the receiving end of one last week and it packs a punch. My
grandchildren had a good laugh at my expense as I thought it was a toy
tennis racket. Certainly made me jump so hate to think of the effect on a
small fly.
We tend to get the flies around the compost bins and occasionally in the
house but generally just ignore them as they do no harm.