A rant about Duracells, I've had a number of batteries leak in the last ten years or so, well before the date on the battery. They have all been Duracells. The old "Copper Top" has been a leaker in my gear. I use Rayovac or Eveready in my 20/20's!
I just checked the 9V pack I bought at Costco a few months ago. Duracells. I'll have to start paying close attention. They're inm my smoke detectors and basement water alarms.
I'm amazed noone have made a HI-FI 9V battery with gold contacts for ultimate sound transfer.
Or how about a vintage one for guitarists, with tweed covering and rusty poles to get the right 'brown notes'?
You never know what someone will come up with. There will almost always be people who will believe the hype.
I once bookmarked a parody site (no longer online) which claimed to be selling a tiny bottle of what looked like clear liquid for about $70. You were supposed to brush it on your connections and it would improve the tone of your high-end stereo, guaranteed. I thought it was hilarious until I realized that it wasn't a parody. Some people must have bought it.