Invisible indexes - you can already do that in SQL Server since 2005 - ALTER INDEX .... DISABLE and then REBUILD to enable it again if you want.
Paul Randal
CEO, SQLskills.com: Check out SQLskills online training!
Blog:www.SQLskills.com/blogs/paul Twitter: @PaulRandal
SQL MVP, Microsoft RD, Contributing Editor of TechNet Magazine
Author of DBCC CHECKDB/repair (and other Storage Engine) code of SQL Server 2005