Backstory: My friend just paid $1200 for a custom knife. $1200... I mean, it's awesome but that's a lot of money for a knife. That got me thinking about other normal items that can be made custom to increase their value.
The Idea: Custom key handles for door and car keys.
Deep Dive: You would need to be passionate and skilled in wood working and/or metal working. The concept is that you would take an ordinary car or house key and make a custom design for your customers.
Validation: The high price for custom knives sparked this one. You could advertise one etsy or a local facebook group to try one or two.
Monetization: This is a slower process with a lot of custom work. Your markup/margins would be quite high. This is not a unicorn idea but it could turn into a profitable side hustle.