Drop all tables from database command apart from named few
Using such a CURSOR, you can print or execute all the DROP statements:

DECLARE cur_del CURSOR FOR
    SELECT QUOTENAME(SCHEMA_NAME(schema_id))+'.'+QUOTENAME(name) 
    FROM sys.tables
    WHERE name NOT IN ('x', 'y', 'z', ...);

OPEN cur_del;

DECLARE @table sysname;
DECLARE @sql nvarchar(max);

FETCH NEXT FROM cur_del
INTO @table;

WHILE @@FETCH_STATUS = 0
BEGIN
    SET @sql =  'DROP TABLE ' + @table + ';';
    PRINT @sql;
    --EXEC sp_executesql @sql;

    FETCH NEXT FROM cur_del INTO @table
END

CLOSE cur_del;
DEALLOCATE cur_del;


This query only prints the DROP statements out. You can uncomment the EXEC line if you want DROP them.

The first SELECT does not look for anything at all aside from what is included in the IN(...) and you have to make sure it does not match more table than what you really want to delete.

In the WHERE clause, you can replace name (table name) by the fully qualify name with schema using QUOTENAME(SCHEMA_NAME(schema_id))+'.'+QUOTENAME(name) NOT IN ('schema.x', ...).
If there is only one schema, you can add AND SCHEMA_NAME(schema_id) = 'xxx' and keep name.

It also does not look for dependencies which may prevent DROP.

If there are Foreign Keys, you can first DROP them using a similar cursor along with this query:

SELECT 'ALTER TABLE ' + QUOTENAME(SCHEMA_NAME(f.schema_id))+'.'+ QUOTENAME(OBJECT_NAME(o.object_id)) + ' DROP CONSTRAINT ' +  QUOTENAME(f.name) 
FROM sys.foreign_keys f
INNER JOIN sys.objects o ON f.parent_object_id = o.object_id
WHERE OBJECT_NAME(f.referenced_object_id) NOT IN ('x', 'y', 'z')
    AND  OBJECT_NAME(o.object_id) NOT IN ('x', 'y', 'z');