Take a Holy Hand Grenade, size it up 300 times, strap it on a cart, and this is the result.
A very simple sound that makes the payload cart go "HALLELUJAH!" before blowing up. Inspiration from Worms' Holy Hand Grenade.
Simply put the "tf" folder provided in
(Drive Letter):\Program Files\Steam\Steamapps\(User Name)\Team Fortress 2\