So, there's a nice little shelf above the tunnel exit in the level Halo from the original game. I took the Sarge up there with me back in 'the day' (when you were knee-high to a grunt), but I'm afraid BigGruntyThirst has outdone me yet again, which of course is perfect in my opinion. BGT got three warthogs, and a whole group of marines up there just for fun. Perfect trick - utterly pointless, full of entertainment - excellent. Stop by his forum thread for a couple of links.