In an interview with Gert Drapers, SQLCMD was mentioned as SQL Server 2005's Easter Egg (Gert: "one of the biggest productivity gains for DBA’s in terms of automation"). I hope that I can pull this feature somewhat out of obscurity :-)
Watch the SQL Server 2005 Scripting Webcast which covers most of SQLCMD's features. And when you're done, check out some webcast resources I posted here.
You can find Gert at www.sqldev.net (and soon he will be roaming the VS buildings).