I remember playing this part of Call of Duty: Modern Warfare 3 fondly. Not because you take control of an awesome remote-controlled grenade shooting robot, but because I died toward the end of the level and had to restart back at the beginning of the robot section. Stupid checkpoints.
However, if you're actually talented at this game (unlike me), there's a pretty good achievement on that level, "Persona Non Grata". What you have to do is shoot down the five enemy helicopters using just your grenade launcher. It sounds easy, but those choppers like to move and throw off your trajectory.
That's where Achievement Hunters comes in. In the video, Mike and Ray show you that it's actually possible to hit the helicopters, as well as give some pointers for those having trouble.