This device gives me electric power and has endless possibilities:
Smoke detectors, teasing people by letting them taste electricity with their tongues, radios, a throwing weapon when you want to attack your relatives or partner, improving life skills; everybody should be able to replace a 9v battery, buying it to show of to your friends that you recycle 'old' batteries, guitar-pedals, solving your science problems, guitar preamps, rc car controllers, small talk prop in social situations (why did you buy that battery, what do you use it for, the design, the possibilities)
Every human being should have a Maxell M9V in their life. :-)
Ps. Only use them when you really need them. In guitar pedals they are the most lazy and unreliable way to get you power. Please use powersupplies/adapters for guitarpedals.