I'll go first.

One that I would buy 20x over:

HIGH END: Vitamix. we use it for so much food prep. It's been a game changer for chopping kale for our salads to shredding chicken to healthy frozen treats.

LOW END: Oxo magnetic measuring cups. Taking these to my grave.

Purchase I regret:

La Creuset dutch oven. I know I'll get roasted for this, but there are so many options that are 10x less, so for those of us having to slowly budget our cooking tools, I wish I had waited a bit to invest in this one and stuck with Lodge.