Sugru - rapid, easy, cheap repair of small, broken things. Suguru is basically a hardening putty - it's malleable when opene, and dries to be hard and durable in about 24 hours. I've used it to repair broken axles on a cart, reassemble broken headphones, re-attach a handle to a hairbrush - minor, easy fixes which save me marginal time/money/anxiety/frustration on a day-to-day basis. There may be other, similar, cheaper products (some appear on the amazon search I just did), but I have not tested them.
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: