This works, but be careful, it will cause data loss to open transactions.
ALTER DATABASE [dbname]
SET SINGLE_USER --or RESTRICTED_USER
WITH ROLLBACK IMMEDIATE;
GO
DROP DATABASE [dbname];
GO
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning