Stainless Steel Butter Slicer
I feel like a butter slicer falls midway between an egg slicer and a banana slicer on the spectrum of legit kitchen tools. Like, it's not that hard to nail your cut of a pat of butter - way easier than freehand slicing a hard-boiled egg at least - and how often do you need to cut an entire stick up front, and into perfectly even pats anyway?
On the other hand, if you're having a party and want to make the butter collection portion of the evening easier for your guests, or if you're cooking or baking something that calls for butter in chunks, a butter slicer isn't an utterly useless and preposterous thing to own. Using a knife to complete the task obviously takes longer, plus can get messy if the butter sticks to the blade. The same cannot be said for a banana slicer, which might be the most superfluous kitchen gadget ever created.
So, yeah. Butter slicer. Not as deserving of a spot in your kitchen drawers as an egg slicer, but way more justifiable than a banana slicer.