Just curious...are there any products that you use that you are set on your brand and can absolutely not abide by any other, whether it be a grocery, beauty, clothing, or other type of item? I know in our house, it has to be Heinz Ketchup. We also go out of our way to bring Goodhost Iced Tea back from Canada. We have tried other brands and they don't compare. We would rather just go without...and actually have, rather than drink any other option. I know that people in some geographic areas can be very passionate about the brand of mayonnaise they use, and for others, it is the ice cream they purchase. Let's face it. Some things just don't taste the same when they are made with the "wrong" ingredient.
Likewise, people seem to have preferences for the brands of any number of items from pens to diapers to socks. There may be plenty of other brands out there, but you know the one that works for you or tastes best and you would rather pay more or choose nothing, rather than buy an off brand. (Or sometimes it is the "off" brand that you find to be the best option.)
Feel free to share the items for which you will accept no substitutes. I look forward to learning about what products I might be overlooking.