1. Near the outskirts of this map is a Helicopter, here is how to climb onto it;

Go to the front. Jump on the gun sticking out about knee level (small run and jump). There is 2 gun barrels to your left (while standing on the first, lower gun barrel). Do a small jump onto the very front tip of those 2 gun barrels. While standing on the tip of the barrels, look at the spot right in front of the cockpit, jump up there and then it is easy jumps to the top of the Helicopter.

You can walk all over it or lay down on the blades up top. Good for sniping.

Note that one of the blades on the top of the Heli is not attached, just levitating in the air. Also, when you jump onto the first gun barrel, there is another about chest height that is just visual, you can move and jump through it to the double gun barrel.

2. House with no roof;

Jump onto the broken wall behind the house, jump up top. This should be obvious. From the top, you can drop inside onto the top of the window (boarded up) and surprise people. Not great, but I thought I would mention it.