You can use a Dremel (or similar brand tool) to both cut the "teeth" section off the key and engrave information on the large section. Similar to a dog tag. You can then use these "tags" for identify pets and belongings (luggage perhaps?) Small key rings are available at most hobby and craft stores, as well as Walmart.
If you know of any small kids who live in a house or apartment that doesn't have a fireplace they may be concerned about how Santa Claus will get into their house. Go on the internet and do a search for "Santa's Magic Key". You can use any kind of key but the larger the better. You run Christmas ribbon through it and print out one of the poems that comes with the instructions. I print out the poem, laminate it, punch a hole and run it through the same ribbon. You may spend about a dollar per key, and you can sell them for up to $5.00. I've been doing this for a couple of years and I always sell a few and give away a few. Good luck!
I made a windchime from some "unknown" keys. I used old house keys, trunk keys, lock keys, etc. I put with the lighter, smaller ones at the bottom of each row and them tied at different levels with fishing line. I hung them from a small piece of driftwood. I used small eye hooks to hang 5 rows of 4 to 5 keys, and 2 larger eye hooks at each end on top of the driftwood. Love the other ideas here too!
Use the top of a 2 liter pop bottle and cut it where to top of the label is. Then poke some holes and hang the keys from the holes. It's a good craft for kids.
I once saw a small box covered with glued on keys. It was really cute. Maybe paint the box black so the silver and gold keys really show up.
Many years ago I saw in a movie magazine a lovely bracelet made by an actress. It was made of a variety of keys, it was very "antique looking" and was really attractive. The bracelet itself was a chain to which the keys were attached.
If you want to keep the drapes and curtains straight - put keys in the hem.
I made a necklace out of part of my collection of old keys. There is 11 keys on the necklace with a one inch space between each key.
A doorbell or a window intruder alarm.
Each using several keys as the clanger.
1-Doorbell drill a hole through the doorknob side of the door frame.
Run though the hole a piece of electrical wire
Secure to that wire a length of fishing line.
Now you make your bell or even a key windchime.
Me I used an old juice can poke a hole on the bottom .cut out the other top ran my fishing line into the can tied and taped the line to a small pencil.
Then I attched and strung 4 keys at different lengths of line. I hung the Key Bell on the joice in the center of my ceiling right off from the living room---Then I secured the exposed fishing line with screendoor eye hooks The small hand screw in kind.
After threading I resesecured the fishing line to loop I made on the eletrical wire.
On the outside I secured on the same type of a loop One of those old Lucky charm /Ceiling Fan ? Rabbits foot chains. Mine was the chain complete with the Rabbits foot.
The slightest pull of the Rabbits foot would set the can to rocking and the keys hitting the inside of the can. ( Oh you can decorate the bell can anyway you like of just use the key wind chime if you want
I simple attached through eyelets the fishing line to the top of the window then attached several keys to the line so that if the window is opn the keys will hit the window glass swaying back and forth a few times.
And There You Go Mr. Thriftys Rootin Tootin Frugal Security System with doordbell