How to list an old manuscript on my CV/website? A while ago, I wrote a short paper and posted it on arxiv. 

My paper contains an observation that some idea in another paper can be used to give an alternative proof of some other result. I like the paper and other researchers have responded positively to it. However, since it neither contains a new result nor a new idea, the paper isn't really suitable for the usual publication channels. Thus I have not published it in the conference or journal sense.

I'm quite happy to just leave the paper as an arxiv preprint and not go through the publication process. However, I'm currently applying for jobs and I think that it looks odd on my CV/website. I list it under "Manuscripts" but that feels out of place, as all the other papers listed there are recent and most are currently in submission. It is "published" in the literal sense of being publicly available, but I don't think it's right to list it under "Publications" either.

How should I list this old arxiv preprint on my CV and website, if I have not "properly" published it and don't intend to?

Of course, one resolution to this is to find somewhere to publish it. But I feel like that is a waste of time (and also too late for the current job cycle).
Just put it in an "unpublished" or "other" section of your publications.