My Ninja and I have lots of secret handshakes and silly routines that we do together. One of my favorites is our "I love you with all my heart" routine. Any time one of us uses the 'I love you' sign, we follow it by making a heart at each other with our hands or (more often than not), he'll have already drawn a heart on the back of our hands, and we'll tap them together all while saying, "I love you with allllll my heart."
IF my little man ever grows out of having silly routines with his mama, (I'm still not convinced that this day will ever come, but if it does...) I will have this permanent reminder of when he would put his little hand up at playtime, at soccer practice or falling asleep, just to let me know how much he loves me.
Some inspiration photos I found on Pinterest.