Gears of War: Act 4 Campus Grinder

You'll get ambushed by a group of Drones and Theron Guards, and just as you kill them, two Boomers will come out of a newly opened door. Shoot at them taking cover in the building. After you finish them off don't approach the door you saw Boomers come out from. You can do that after you pick up 25.Tag lying near the place you started the level at.

Inside you'll run into a Theron Guard, don't think -shoot. Make your way forward, find a sniper gun and use it to help your friends below. If there's nothing left for you, get a Hammer (you'll need to finish off some Wretches first). It's best to swap it for a sniper gun though; losing the machine gun can cost you your life here. Run ahead and use the handle.

There's a sniper in the place you can see on the screenshot. Finish him off crouching below the window. You can use your sniper gun to shoot enemies in the courtyard. After you're done go downstairs. Two Drones will come out of the opposite building - kill them taking cover under a window. You'll also have to deal with two Wretches. Use a sniper gun and take down the crew manning the Troika gun. After that, shoot the propane tank in the car.