We're looking into implementing an issue tracker for our web agency. The problem is that most issue trackers seem to revolve around the assumption that an issue is a bug, whereas in a web agency environment, a lot of the issues (request, or whatever you want to call them) are about changes and additions to a current web site.

It also seems to me that a lot of issue trackers assume that you're working on one main software project, and uses that project as the focus of the tracker. A good issue tracker for a web agency would be one which puts each separate client and their issues at the heart of the system, making it easy for them to track and report issues.

Does anyone know of a good issue tracker for the web agency workflow? What are other people using?