Digital art

  • Clip Studio Paint - closed source, but extremely powerful painting and illustration software with an EXTENSIVE assets library that is regularly updated by other CSP users. You buy it once and it often goes on sale. I highly recommend it over anything else on this list.
  • Krita - free + open source painting software. I'd go for this one if I couldn't afford CSP.
  • Medibang Paint Pro - freeware. Comparable to Krita and CSP.
  • Autodesk Sketchbook - one of Autodesk's very few free programs
  • Procreate - iPad exclusive, but great app if you can afford Apple's overpriced products.
  • Paint Tool SAI - lightweight painting/illustration shareware
  • Fire Alpaca - comparable to paint tool sai
  • Petallica Paint - AI web app that colors sketches/lineart, this is built-in to newer versions of Clip Studio Paint.

Pixel art

2D Animation

  • OpenToonz - free + open source program used by Studio Ghibli.
  • Pencil2D - open source
  • tvpaint - closed source
  • Clipnote Studio - recreation of Flipnote Studio, the animation app on the Nintendo DSi.
  • Storyboarder - free + open source storyboarding software

3D Modelling + Animation

  • Blender - free + open source. you can model, render, and animate with it.
  • Wings 3D - free + open source. more simple than blender.
  • Autodesk Maya - disgustingly expensive.
  • Crocotile 3D - makes simple 3D models from tiles
  • VRoid Studio - free. specifically for making VTuber-style avatars
  • picoCAD - tiny modeller for tiny models

Photo editing

  • Adobe Photoshop - Adobe sucks ass so pirate it. If you're not going to pirate it, don't bother.
  • GIMP - free + open source image manipulator. Often cited as the closest alternative to Photoshop, which I agree with. However I have extensive experience with both of these programs and I've always preferred Photoshop. Go for it though!
  • Photomosh - edit photos using WebGL
  • Remove.bg - automatically removes backgrounds from images

Vectors

Other programs and tools

  • ezgif - online gif creation and editing
  • tinypng + png crusher - image compression
  • waifu2x - image upscaler. works best with anime artwork.
  • Flowscape - allows you to create tiny environments by dropping 3d models into a landscape.
  • Death Generator - create custom game over screens
  • Trianglify - generate a custom geometric pattern
  • Error Message - create custom Windows error messages
  • WordArt - make 2000s Microsoft Office WordArt

Assets

Stock and images

Fonts and typography

Color

Human anatomy