Redmine

If you set the administrator flag for your regular user then you should not need to log as admin.

I disagree on the fact that admin rights should be restricted ...

well but why should an admin have all rights in all projects, maybe he is only there to manage users or add new costum-fields and should not have the right to everything

The point is, that an admin does not need rolles, but in fact admin is also some kind of role, BUT the role of an admin does not nessarly include having all possibilities

I like the admin flag how it currently is: it resembles the root user on Unix. So it has every right and can do maintenance without messing with permissions.

What you do probably want is something like a global role concept (as described in #4427). That way, you could give a user the right to just create a new user but nothing more. However, I would not want to restrict the admin users in anyway as this would be unintuitive and would hinder the workflow for most people.