My favorite is an immersion blender. I have a cord free model. I like to use it making sauces and eggs.
Sauces to hide veggies from my toddler who doesn’t realize the veggies are there for fortification and health.
Eggs I like to blend/whip air into the scramble. Cheese is an easy add too. They are super fluffy and delicious.
As far as cleaning it, I wipe any missed chunks off, put warm water plus soap in a cup, and blend til stiff peaks, JK.
What is your favorite kitchen gadget?
I just posted a link to this sharpener which I love in another comment.
Some of the dull but high quality knives I had took a bit to get sharp first time (under ten minutes though).