There is an encoding list in the Buffer API doc: ascii, utf8, utf16le / ucs2, base64, binary, hex.
However the lists in the File System API doc for streams are not complete.
fs.createReadStream:
"The encoding can be 'utf8', 'ascii', or 'base64'."
fs.createWriteStream:
"The defaultEncoding can be 'utf8', 'ascii', binary, or 'base64'."
In the both lists the "utf16le / ucs2" encoding is misguidingly missed.