I'm not sure if it counts as brand, but for eyeglasses, I stick with zenni. Just this past weekend, because they were buy 1 get one free, my wife and I picked up 4 extra pairs of glasses.
For toilet paper, I almost exclusively get Scotts, and for paper towels, almost always Bounty. They really are better than the other name brands.
Costco/Kirkland Signature
Yeah, I guess that's about it for me.The only ketchup I'll buy is Heinz. That's a close as I get to exclusivity on anything.
...Brownberry and my toilet paper...