Pixel Art Studio - A purpose-built drawing tool for pixel artists
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Pixel Art to CSS - Draw and animate pixel art, export the results to CSS
JS Paint - JSPaint is a web-based Microsoft Paint remake
Juice FX - Easily turn your pixel art into VFX for your video game.
KiddoPaint - MS Paint in your browser (with emojis 💃😽🎨)