Spiked dog collars were invented in Ancient Greece to protect dogs throats from wolves!

Dog collars originated in Ancient Egypt, where of course, they were worn just because they looked wicked. Needless to say, only the very wealthy were able to give their dogs neck bling. Pharaohs had so much money they became bored of wearing jewelry all alone, so they had to glam out their pets too.
It wasn't until the period where Ancient Greece was one of the top civilizations in the world that dog collars had a practical use. Dogs were used on Greek farms, and wolves commonly raided farms in order to eat smaller dogs, sheep, and cattle. Farmers were tired of their dogs throats being bitten, so they put spiked collars on the dogs to stop wolves attacks!
Not only do dogs with spiked collars look tough as nails, but they were apparently very effective in warding off wolves! Unfortunately, the dog collar took a turn for the worse when modern day Goths started wearing them.
(Source)