Anything food related. I'm very snobby about where I shop, what brands I buy. And the list is too long to.. list.
I love saving money, but I also try and keep from purchasing national brands. If I am undecided on what product to buy, I'll narrow it down and read where the product is manufactured. Whichever is closer to home I'll pick.
But I've a thousand rules and exceptions that influence my decisions. I'm very picky about quality.
For example, I've researched nearly every olive oil brand available to me. Olive oil is the first place I'm willing to spluge, and the last place I'm willing to cut on quality. I'll eat dirt foraged from the forest before I buy shitty olive oil. Bertolli is garbage and if I see it in your kitchen, I just may silently judge you with an inferior palate and lack of care for your meals. You mine as well buy canola oil at that point. I'm working on being less judgemental, but lord. I guess olive oil is the most important to me.