The 'very low quality' flag on questions, at least in its current form.
There is no consistent guidance on how users should use this flag on questions, or how moderators should handle them. Some will just close the question, marking the flag helpful, others will say only flag as 'very low quality' if the question needs to be immediately deleted, yet others will say not to use the 'very low quality' flag on questions at all ever.
The flag pushes questions into Low Quality Posts, or Triage, which then either results in closure directly or the question going to Close Votes, which could have been accomplished already via a close vote/flag.
The flag description is somewhat vague:
This question has severe formatting or content problems. This question is unlikely to be salvageable through editing, and might need to be removed.
What constitutes salvageable through editing? Arguably any closable question for a reason that cannot be easily fixed (by the author or community) is unsalvageable, but again, we already have close flags/votes for that.
I am not saying this flag on questions has to go, but the current form is quite useless, and needs serious revision of not being removed entirely. For example, the flag could be designated for questions that need to be deleted by a moderator immediately (posts that just have to go but are not immediately spam or abusive), and that is the policy enforced network-wide.