Query below summarizes default constraints in a database listing all distinct default value definitions for columns with the number of their occurrence.
select con.[definition] as default_definition, count(distinct t.object_id) as [tables], count(col.column_id) as [columns] from sys.objects t join sys.all_columns col on col.object_id = t.object_id left join sys.default_constraints con on con.parent_object_id = t.object_id and con.parent_column_id = col.column_id where t.type = 'U' group by con.[definition] order by [columns] desc, [tables] desc
Different default column definitions in AdventureWorks database: