The theme seems to be compilers, chips, and AI...

• An AI agent that can autonomously design inference chips
• A programming language for an optical computer
• A photonic O(1) MATMUL accelerator
• Compiler for the Jack programming language
• A Regex interpreter using Brzozowski derivatives
• A handwritten tensor algebra compiler with a sparse tensor storage system better than NumPy
• Toy interpreter for RED, my first programming language
• AI chess engine
• Sudoku solver
• CV algorithm to count physical money (from scratch)
• edge detection (from scratch)
• tiny neural net (from scratch)
• Othello engine
• augmented reality chessboard
• cipher cracker
• AI Tetris solver
• train stuff
• toy syntax analyzers
• Graham scan
• hands-free computer interface
• puzzle solver
• Calibron engine
• word ladder solver
• image vectorizer
• search engine
• file storage app
• online word processor
• a toy Quora
• AI for the Ghost word game
• A bunch more unfinished things, and there's probably stuff I forgot to upload to GitHub

P.S., I also made an electric guitar from scratch, and a few EMP generators.