Akalabeth clone for C64 I started working on few years ago, written in 6502 assembly code. Unfinished, of course, and latest source code was lost on hdd failure. Managed to salvage this from different computer. No RNG dungeons, no monsters, no items, but you can roam around in pseudo-3d environment and make hardcoded maps.
Assembler I used for this was KickAssembler.