Consider the following scenario:
A MOSS 2007 Portal where everyone has read permissions but some 'content owners' have elevated permissions on libraries and lists and want to save a list as template (.stp).
In this case they need to have elevated access to the List Template Catalog (http://sitecollurl/_catalogs/lt). Minimal permission level for a user to save a list to the List Template Catalog is: Manage Hierarchy
In a MOSS 2007 Portal (based on the Collaboration Portal or Publishing Portal template) there is by default a SharePoint Group "Hierarchy Managers" created for this purpose. Alternative is to set list-level permissions on the List Template Catalog.