This tutorial will teach you how to use the input/output system to make a combine break a ceiling window and rapell down for a flashy entrance.
Posted by Silverfisk on Nov 9th, 2009
This is actually a pretty simple thing to do, you place a npc_metropolice somewhere and change the property "Waiting to Rappel" to "Yes" and give it a name.
Then you place a brush with a glass texture, tie that brush to a func_breakable entity, change the property "Prop Data" to "Glass.Window\" and give it a name.
After that you just have to give a trigger of some sort the output "BeginRappel" for the npc_metropolice and "Break" for the window and you've got your flashy entrance.