Halo 3 - GOLD SKULL: Tough Luck Skull
Tough Luck Skull
Location: Tsavo Highway
After you pass the shield that blocks the road, you'll reach the Tsavo Highway. An enormous Covenant ship will fly overhead, and at this point make your way towards the large pipe to the left of the highway. Jump down onto the grassy area right below the yellow ladder connected to the pipe. Jump further down onto a gray platform which will have a very narrow ledge connected on the right. Jump onto this tiny ledge, and from here jump onto the much larger platform on your left. Walk all the way down to the end, and on the left hand side you'll see a rock cliff with the skull. Make the long jump over and grab it.
