Elspec (talk·contribs) aka (see the history of Elspec Ltd., if it's still there) 199.203.94.97 (talk ·contribs) adds references to Elspec Ltd. and the commercial site elspec-ltd.com not always in an appropriate manner.
Igni (talk·contribs) makes "grammatical" and "style" corrections in articles which seem (at least to me) to change the meaning, possibly due to a different understanding of the English language.
12george1 (talk·contribs) creating multiple subsections, mostly in tropical storm articles
AndrewCrogonklol (talk ·contribs) weird vandalism, including that of his block notice.
Banned sock of banned user
Voortle (talk·contribs) creating unnecessary articles, redirects, and sections in year and number articles. (I thought he'd gone.)
Hemanshu (talk·contribs) damaging year articles; creating bizarre changes in month groupings, adding (usually improper) explanations for notability with almost always improper italization, adding Afro-xxx to nationality (often wrong, never appropriate)
hopiakuta (talk·contribs) has some sort of screen-reading software which causes destruction of information when he tries to edit.
81.214.68.90 (talk·contribs) adding interwiki links to non-existent tr.wikipedia articles.
Global warming / climate change
current list (from 12 January 2012 or so) maintained at User:Arthur Rubin/IP list. Editors are welcome to add (but not subtract) from the list. — Arthur Rubin(talk) 15:42, 2 February 2012 (UTC)
99 anon (and 97.87.29.188 and 209.255.78.138, 108.73.115.71, 216.250.156.66 and possibly 24.11.21.141) adding easter eggs, inappropriate #See also and {{seealso}} links, and clearly inappropriate categories to many global-warming-related articles. Although "it" is clearly a single person on a floating IP, it seems not subject to 3RR. Style factors in favor of their being the same person include:
It used to link 350.org whenever the number 350 appeared in a Wikipedia article, as well as linking to any and all climate change articles from350.org.
Using "also see" instead of "See also" in section headers and in text.
However, I am subject to 3RR, so I'm noting (some) of the articles in which they are adding this material. I suspect the only solution is to permanently semiprotect all climate change articles, broadly defined.