I gave my husband an extra set of keys on a unique key chain.  I took a normal key ring and put a eyebolt on it instead of the normal ugly plastic
thing.  Then I painted  3 different nuts.  I painted one red (passion) to represent me, one blue and one green for our two boys. 

When the paint was dry I put the nuts on the eye-bolt.  I gave it to him with a note, "We're nuts for you!".  It is extremely easy to do and you can get the nuts and eye-bolt anywhere.