List box control with a single selectable value.
For stable and predictable behaviour, always use an explicit ORDER BY clause.
The name depends on the usage. If the control is used to retrieve values from a lookup table then the procedure should be named "<Schema>.<LookupTable>Dropdown". If it is not and the values are not directly linked to rows in a table or the functionality is specific for the current field (say for instance a choice between each of the last six years) then the procedure should be named "<Schema>.<Table><Field>_Dropdown".
The suffix "_Dropdown" should be used since the control works exactly like a dropdown regarding result sets from the SQL call and naming the procedure in that way enables you to change field type without renaming the procedure.