Tinykl. It's tiny, as you'd expect, and works extremely well. Oh, and it's
free.
http://home.rochester.rr.com/artcfox/TinyKL/

Avast reports it as malware - win32:trojan-gen (other) - there`s a
chance it isn`t I suppose, but all keyloggers are classed as malware
these days.