Change all database owners on a SQL Server to another on a server in one swoop. Scary but it works.

change_all_owners.sql

USE master
GO
DECLARE @sqlBase nvarchar(300) = 'ALTER AUTHORIZATION ON database::XXXXX TO sa'+char(13)+char(10)
DECLARE @sql nvarchar(max)=''
SELECT @sql = @sql + REPLACE(@sqlBase,'XXXXX',name) from sys.databases
	where name not in ('master', 'model', 'tempdb', 'distribution', 'msdb')
EXECUTE(@sql)