Tools from Itch which I think are pretty cool but aren't essential in a way.
Automatic tile setter
Tile-based 3D scene creator/editor
Pixel brush set
Random art generator, similar to https://www.random-art.org/.
Bauhaus-inspired art software
Neat procedural gun generator.
Procedural gun generator made with TIC-80. I actually ended up making an asset library based on the parts used in this tool, which also allows for a lot of creative freedom from the user.
Procedural weapon generator for GameMaker Studio.
Motion graphics editor.
"Every time I see the little symbols in a lot of SumaQosh's images, I always think of runes." - focalflare
Procedural rune generator.
Successor to Flipnote Studio.
Free and open source (on/off)line pixel art editor.
Procedural sigil generator. Maybe make any of the generated sigils you get your next music producer emblem? 😉