We had a tester/QA person like this for a project, an older lady who knew the domain at hand, but not so much about computers. She'd find the craziest bugs and produce amazing stack traces, mostly in the last week before a release was to go out. By the last week before release, it took the program manager 2 minutes to see that the bugs were not worth fixing...
I worked with a dev who was assigned to a full-time QA duty by the management. Sort of development pre-QA tester if you will. Guess what? He filed over 200 (<i>two hundred</i>) bug reports within a couple of weeks. <i>Major</i> ones. Other devs never complained, the management was ecstatic, but the guy still quit few months later because they refused to release him from QA duty and back into the development.