Either my Sanyo Talkbook recorder (used for lo-fi field recordings), or my modified Walkman.
The Talkbook takes standard cassettes, and the built-in microphone seems to have a really nice filter that cuts the high-end in a deliciously warm way.
The Walkman, which I'm still modding, has gone from being a generic tape/radio device and turned into a horrendously harsh noise machine, perfect for HNW and also for getting random samples from frequency sweeps.
The hardware I've got is largely self-built, so it's replaceable/fixable without too much hassle.