Here is a first person view of a critical choke point in the game Black Hawk Down by NovaLogic. The game type is Attack/Defend, and the map is Urban Raid. This point allows a gunner to put out a constant fire that blocks the defenders from the targets. Once the defenders are held back from reching the targets, the attackers can easily make their way and destroy all of the targets. There are other points on the map to accomplish this, but this one single point being held by a gunner will usually lead to a quick win.
This is the map view of the same spot. The blue dot is the defender's spawn, the red dot and black line is a gunner, showing the line of fire to hold the defenders back. The three red dots in the center are the remaining targets. The green line is the waypoint to the fourth target. If the attackers are advancing to the targets, the longer the gunner holds the spot, the easier the advance is, and the more targets that will be open to attack.
The defenders will have to outflank, nade or somehow take on the gunner and stop him, or the game will quickly end.