In FogBugz 7, I had groups setup in FogBugz with several projects assigned to them. I would love to be able to create a milestone that could be used for any project that is associated with a given group. This would prevent me from having to create the same project-level milestone for all my group's projects. I suppose I could use global milestones, but then I'd clutter things up for all the other groups that don't care about my milestones.
Update for FogBugz 8: Because groups have changed and no longer map directly to projects (see this post on bringing back groups OF projects), this multi-project-milestone feature will need to allow you to choose a list of Projects for a milestone.