Mildly amusing:

A complete stranger accusing you of having “no balls” in a comment to your blog

Amusing:

That the comment was a perfect example of the sort of nonsense your post was being critical of in the first place

Just plain funny:

The next paragraph starts: “Don't want to be rude but...”

Update: In a nice display of synchronicity, I just noticed that Mark Pilgrim's diveintomark now sports the following button on its comment forms:

I certify that I am mature enough to participate in this discussion

(Note to self: need comment permalinks)