Valve cap with built in stem tool
 

...and I feel foolish.

A few weeks ago I installed some new tires and tubes on my MTB. They were pre-Slimed tubes. I put the valve caps in my pocket as per SOP. I pumped up the front just fine and put the cap back on, then on the back I got some Slime in the valve stem as I pumped it up and it wouldn't hold air. I re-pumped it a few times hoping it would hold but I was out of time and had to put stuff away. The valve cap has been migrating from pocket to nightstand and back for weeks as I keep telling myself I'll remember to get back to the project some time when I'm out in the garage. I felt it in my pocket today and pulled it out - it has a valve stem tool built into it. I haven't tried it out, though. I put it back in my pocket.