Have some of you heard yourselves?
Shooting cats with BB's, thats illegal, causing unnecessary suffering.
Concealed sharp spikes such as gripper strip, tacks, glass - illegal, causing unnecessary suffering.
Bamboo skewers in the areas they poo - and when your toddler faceplants into them?
Jeyes fluid needs to be rinsed off, it is horribly toxic to animals AND to humans, and not just ingesting, but skin contact too - you definitely do not want that stuff around kids and putting it down neat, where you know animals will go is again illegal (causing unnecessary suffering).
In your eagerness to inflict suffering on animals who are only behaving as is natural to them, because their owners are irresponsible fuckwits, you're actually happy to break the law and put your own kids at risk too?!
Effective and safe solutions:
Harmless deterrent - motion activated water sprays, a dog that will chase but not catch..
Preventing entry - rollers on top of fences and blocking gaps under them (for gates a heavy bit of carpet offcut or a roll of chicken wire (flexes as you move the gate but too stiff for a cat to get under).
Small yards/gardens can be netted off with heavy duty bird proof netting.