Q:

work-item tracking tools with drag-n-drop stack-ranking?

I'm looking for a work-item-tracking/bug-tracking system (or JIRA plugin, or TFS plugin, or...) which makes it easy to stack-rank work items without having to manually assign priority values to each work item.  
Instead, our team wants to be able to see a list of open work items and be able to drag-n-drop one or a multiple selection of work items until the order matches the team's prioritization.  This would be much easier than arguing about priority numbers and dealing with ties (e.g. "which of the 5 bugs marked priority=2 should I work on today?"). 
Our team is considering switching work-item-trackers (we use Gemini now) and availability of a good drag-n-drop prioritizer is high on our requirements list. 
I realize drag-n-drop ranking is non-trivial because no team will stack rank all work items. Instead, we'll want to take a subset (e.g. work items for one sprint sprint or iteration, or bugs assigned to one developer) and stackrank those, then later look at a different subset and stackrank those, etc.  And I'm sure we'll sometimes need to mix and match different stacks, so there'd need to be heuristics (ideally configurable) about how to show a stack of items previously stacked separately. 
Pivotal Tracker is close to the drag-n-drop UI I'm thinking of from a UI perspective, but Pivotal's model of separating user stories from the underlying work items (plus a few other issues) doesn't match how we want to work.  We don't want to have to deal with different artifacts (stories vs. JIRA/BugZilla work items)-- instead we just want a drag-n-drop UI to automatically fill out a "priority" field in the issue tracker, and which we can use later when sorting and filtering.  And we wouldn't want to use Pivotal as our only work item tracker, because it seems to lack common features like bulk editing which are critical for large projects. 
Anyone know of a tool like what I describe above?

A:

Urban turtle is the best TFS add-on, making ranking/prioritizing a sane activity.  Priority by number is a disaster so don't think you're alone there.
http://urbanturtle.com/
Urban Turtle is updated every month and used by quite a few teams including a number of my teams.

A:

Eylean Board has what you are looking for. They offer a task board where the tasks are prioritized by moving them around, the priority tasks being on top. Interface is nice and clean and they offer other features such as integration with TFS, reports, etc.

