Just a few I've encountered (from Pathauto):
blog, blogs, Pathauto

And the names of some of the WYSIWYG editors used on Drupal sites (also from Pathauto):
bueditor, fckeditor, htmlarea, htmlbox, tinymce, whizzywig, widgeditor, wymeditor, wysiwyg, xstandard

(It would also be great if "An unknown or misspelled word has been detected on this line." would actually report which word(s) it doesn't like... but I guess that's for anothing feature request. :))