I use Paint 3D since I haven't realized I'm going to need better software yet.
Super Mario Boards
Cloudwalker
Hint Toad
If you are looking into drawing things digitally then I would definitely recommend Krita for raster art. Actually, I lean towards not using any digital tools for drawing my line art. That's just my preference. After I finish my line art on paper, I scan it into Krita for coloring and minor touch ups. Krita is completely free, and has an online manual. If you have any specific questions related to Krita, I'd be happy to answer them!
For vector art I would suggest Affinity Designer and Inkscape.
For vector art I would suggest Affinity Designer and Inkscape.