I'm beginning to think that I am the only person on this list that
hasn't listed mine yet, so here goes ....
a cheap mandolin slicer that I bought for $20 at my local grocery store,
now I can make a whole cookie tray of super thin potato slices (to be
baked into chips) in about 5 minutes, or slice enough vegetables for an
entree salad for 2 in about the same time.
My vegetable peeler with the vegetable brush on the other side. I keep
it hanging over the sink so I always know right where it is whether I
need to scrub or peel my veggies.
And, last but certainly not least, a good nonstick pan (the kind that
you couldn't stick anything to if you tried) and a nonstick pot with a
tight lid for cooking rice (nonstick is really important if you forget
it and burn some to the bottom ... it just lifts right out).
Those really are the only things I absolutely use consistently and can't
imagine going back to living without.