Ten years on (!), a couple more items that seem to keep coming up in conversations about kitchen equipment:
Dishers, aka "ice cream scoops", are actually much better for portioning cookies and muffin batter than they are for scooping ice cream. (Get an ice cream dipper for that.)
Oven mitts. Whyyyy do so many kitchens seem content to suffer without these? So much easier and safer than using tea towels.
Funnels. Avoid waste & frustration when putting stuff into jars or bottles. In particular, you can also get wider-mouthed funnels for putting stuff into mason jars -- search for "jar funnel" or "canning funnel".
Bottle brush. An absolute necessity when it comes to handwashing glasses, mason jars, and the like. Never curse being unable to reach that stuck-on junk at the bottom of a glass again!
Rolling pin. Not generally needed if you don't do the baking tasks it's needed for...and honestly, if you need one, you probably already have one you like. That said...while the style of rolling pin that's best for you is going to depend on how your particular hands / wrists / grip strength / etc, please let me put a plug in for my personal favourite, the french rolling pin. I find it gives much better control and much more even pressure than the handled roller type, and it's a hell of a lot easier to clean up in the sink as well.
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Ten years on (!), a couple more items that seem to keep coming up in conversations about kitchen equipment: