I wrote my first chess-playing program in 6502 hex because I didn't have an assembler, and I still remember some of its opcode values all of these years later. Such a fun little chip!

Chess? Wow. I did some 6502 programming in hex on my Atari 800XL, but just for simple things like display list interupts. I had a list of all the 6502 opcodes and hex encodings from a magazine or book and figured it out from there.