Leatherman. Sent them my many-years-old PST, told them I broke the screwdriver tip through what was unquestionably abuse, and asked to be billed for the repair. They not only fixed and returned it for free, they upgraded several of the other tools to the latest design and lubed and cleaned it, too.

Broke my Sweetwater filter, and the maker sent a replacement for free, no questions, no proof of purchase, no postage, one phone call, all handled by the guy who answered the phone.