Since someone already mentioned electric guitar, I'll go with: Petzl Grigri 2[1] I was initially pretty skeptical of Grigris. Climbers have used far more primi

Since someone already mentioned electric guitar, I'll go with: Petzl Grigri 2[1] I was initially pretty skeptical of Grigris. Climbers have used far more primitive devices for a long time, why do I need a big, bulky hunk of metal and plastic to catch falls? But now that I have one, you'll have to pry it from my hopefully not cold or dead hands. I don't need to have a death-grip on my rope if my climber is hanging for a while. I can go hands-free on rappel to get stuck gear. Most importantly, it has certainly helped prevent some accidents that could have been catastrophic--one particular incident left me with a broken foot, but without the braking assistance from the Grigri, I may have instead walked over to a cratered climber. Best $99 I've ever spent. [1] https://www.petzl.com/US/en/Sport/Belay-devices--descenders/GRIGRI-2 https://www.petzl.com/US/en/Sport/Belay-devices--descenders/...