What’s the tag that you see misused most often? In my experience, it’s “solo.” I very frequently see either blatant multi-subject art mis-tagged as “solo” or else see art with disembodied parts from a second subject still tagged as “solo” even though this is clearly against the tagging specifications.

Most probably tagme. With the amount of implication chains, most posts already exceed the minimum 12 tags required to qualify for tagme, plus the inherent uncertainty as to why the initial tagger had added the tag in the first place.

Even if not my personal vote for this (it would probably be zero_pictured), there is a wicked amount of misuse of *_text in terms of languages when shown alongside translation_request (or basically anything -translated. For one of the more vital tags employed in the "furry art archive" part of E6/E9, it sure needs some scrubbing every once in a while. Can't blame anyone, though; these things are natural, and even many trained eyes would take some time with some examples of chinese_text/kanji confusion, or non-Russian cyrillic_text. Worst of all, though, is the complete lack thereof of *_text that is way too common. Why? At least give it a shot, you're much more likely to connect the writing system to an expert even if you end up being wrong.

Bound in case of character restrained by tentacles. There's at least one new misstagging every day on the new posts.

humanoid beats all, I think. How many of the tagged posts have nothing but anthros?

Not the worst offender numerically, but the implication of older_* and younger_* to age_difference has wreaked havoc upon the latter tag. So many people don't understand that older is not a synonym for old, and ditto for younger and young.