For a children's birthday party, a lego brick keychain sounded like a fun giveaway. An official one can run $8. Let's see what we can do with less than $20 in parts. Get a length of chain.
Use pliers to break every sixth link, so you end up in chain sections of five links long.
Drill a small hole in one end.
Thread a small key ring through.
Thread one through the chain.
Attach to the brick.
The finished product.
An alternate way to attach. Makes it more stackable, but is harder because you have to line up the holes, and threading the ring through is much harder.
Work complete, with parts to spare, in about half an hour! Much better than spending $128.