Misaka imouto 10032 from Toaru Kagaku no Railgun's adopted stray black cat.
Often called "Dog" by the fan community, its lack of a firm name is actually a bit of a running joke. Misaka 10032 first names it "dog" as a joke, then "Tokugawa Ieyasu", and "Schrödinger". Kamijou Touma doesn't agree to any of these as a good name for a cat. She then agrees to put the matter of naming the cat on hold, and it's thought she might have literally named it "保留" or "on hold" at that point. The cat is often seen with Misaka 10032 and is occasionally important to the plot of the series.