I suspect that this recommendation will be redundant for many or most of LessWrong, but let it be repeated: buy a good basic multitool and keep it where you can easily find it. Better, buy a couple of them and keep them (say) in your car, in your desk at work, and at home.
Sometimes you need exactly the right tool for the job. However, for many simple tasks, and for any emergency, the simple tool immediately at hand is much more useful than the ideal tool which would take time and effort to retrieve.
What would you recommend?
I have a Leatherman Squirt E4, which is never the right tool for the job, but always available, and complies with UK knife laws. I also have very good experiences with the Leatherman Wave, but don't carry it around as a matter of course for aforementioned knife-law reasons.
I have often benefited from recommendations for Things I Didn't Know I Wanted.
Given that Less Wrong is a community of unusually intelligent, critical, and self-improvement-focused people, I suspect we can generate a pretty helpful thread of product recommendations — perhaps even a monthly thread of product recommendations.
Rules: