Wandering Daisy wrote:"that heavy car key" weighs 0.6 oz. I carry my car key and make up for its horribly heavy weight by deleting four peanuts or carrying one sip less water.
Some of the electronic keys weigh twice that. They really are kind of clunky.
I usually carry my key but I have also left it behind when I was trying to trim everything I could. I walked the JMT a couple of years ago without any resupply. I went over everything with a fine tooth comb. I wouldn't have wanted to give up those "four peanuts" because I also trimmed my food to what I thought was a minimum. Yes, on one level worrying about 15g is ridiculous but if you have that attitude about everything in your pack it has a funny way of adding up.
I weighed the several $20 bills, my driver's license and the credit card I took (total 15g). I neglected to bring the park pass and the guy who gave me a ride didn't have one. That tiny savings in weight cost me one of those twenties!
Normally though, I've got the key. And often a few cans of beer too.