When you manually add a registration for an event in CRM, from the Event's 'Registrations' tab, you fill out the Registration Option, then the Registrant, and then see the checkbox for Waive Registration Fee.

This Idea is to be able to query on registrants who had their event registration fee waived via that checkbox. This should be a 'Fee waived?' field in the Ad-hoc query type of Registrants, as well as a field in the Event query type.