Knife sharpening service. I personally don't need it...I am kind of a freak about keeping a sharp edge on my blades but that would be a nice service to offer people.
Picture this...Guy walks in off the street, guy behind the counter strikes up a conversation and at some point it goes to knives.
He asks the customer, what kind of knife do you carry?
Customer answers. Been carrying this Benchmade for some time. He pulls it out.
Would you like us to throw an edge on that while we talk? No charge...
Wow...sure thanks!
Now you tell me...would that customer tell that story to his buddies? Darn right he will...
Be sure you have someone who really knows how to sharpen by the way...If you screw up that customers knife he will tell that story to. (And yes my services are available...

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One other thing. I hate walking into a gun store and feeling like I just walked into some good old boys club.
Like the music stops and everyone turns and just stares.
How about no matter what everyone is greeted and asked if they could be helped.