I will only buy milk from the local (well ok regional) milk store, Kawartha Dairies.
I mostly only buy electric fencing (tape, rope, etc) from Premier, because I think they carry excellent quality *and* because they perpetually develop and import wonderful new products and should be encouraged
I will also confess to being strangely stuck on Pace Chunky-style Salsa (medium, and I add vinegar and a little sugar before using

) and on Presidents Choice brand dark chocolate bars with almonds (for Canadians I highly recommend this as absolutely the BEST chocolate for the price). But there it's more the products I'm loyal to rather than the brand in general, if you know what I mean?
There are some brands I am ANTI-loyal to. For instance, after a variety of experiences with Sears that I will not detail here for the sake of my ongoing mental stability, they are not getting one more penny of my money or second of my time, NO MATTER WHAT, EVER.
Frankly enough of the non food stuff I buy comes from thrift stores that you can't really BE hung up on a particular brand
Pat