Area: Hoover Dam
Category: Throw stuff
Vehicle type: Either
Goal: Get the most air time for stuff you throw in 90 seconds
Score for Gold: 1218

Strategy #1:

Go to the middle of the dam (in between two vehicle spawn points) and throw the cars that come to you over the side.

Strategy #2:

Go quickly (in vehicle mode) past the east intake tower and transform to robot mode in front of the west intake tower. This turns out to be a good spot to take advantage of vehicle spawn points. Throw them over the dam as they come to you, if you don't see one handy just spin in place with the L or R button and one will appear. Be careful not to throw the cars at the other cars.

Strategy #3:

It turns out that if you throw something over the dam, it leaves your proximity and stops adding points long before it reaches the bottom. If you jump over the side of the damn and follow it down, it gives a lot more points. Then fly back up (should be faster using the jet's R-button speed boost). Not sure at the moment if the gained points are worth the trade off for the extra time taken per car. However, if you stay on the dam until just before time runs out (about 8 seconds left) and you only jump off and follow the last car down, you don't need to worry about getting back up there.