This post has been closed as a duplicate. All votes have been moved to the original: Pull Users into Custom Forms
Create a custom field within a custom form that is able to pull system information.
Take as an example the "Project Owner" system field which pulls a list of users within Workfront. Use case: Say that the Purchasing department requests a custom development to be done - The "Project Owner" is assigned to a member of said department and you can assign an "IT Leader" within a custom field so that both functional and technical parties can be accountable.