TP for sure, but generally speaking, you get what you pay for (so I'm willing to pay the extra for better quality, especially in things that are going to be well used).
Camping and biking gear. The proper gear lasts longer and makes those activities much more enjoyable. I can't afford super high end stuff but I definitely don't go cheap.
Almost anything electronic or mechanical. I don't care so much the brand, just that I get quality. Seems I save money and headaches in the long run. Oh and the OPs answer, never go cheap on TP.
Hunting items to a degree - Ill buy all First Lite / Sitka clothing , 600 dollar rifle scopes and 200 dollar bow sites then by a 50 dollar tree stand and a 30 dollar trail camera.