I'm a huge fan of Dashboards for spotting potential ticket issues (missing values, misconfigured fields, etc), and I have a dashboard that opens when I start my PC every day, with a whole battery of 'negative' widgets.
By that, I mean that I proactively look for bad behaviors or problems that you may have to deal with later. When the dashboard opens I hope to see a bunch of "No Data available" results, but if anything does return I know I have to do something with it.
Open but Unresolved bugs:
statusCategory = Done AND resolution = unresolved
This widget is just looking for when some has closed a ticket, but hasn't assigned a resolution value to the ticket. Most often this occurs when someone adds a new project and hasn't properly configured their workflow (post functions, popup screens, or automation rules)
Incorrect Link type for Initiative tickets
project = Enterprise AND "Initiative Ticket[Short text]" is not EMPTY AND "Initiative Ticket[Short text]" !~ "EB*" AND statusCategory not in (Done)
(this one is set up for us to make sure dependencies are tracked using the Structure plugin, which relies on the link type to determine hierarchy)
Do you, fellow Jira admins, have any favorite "Oh this is going to be a problem..." type queries?