Walker 2000

The Walker 2000 is a large walking robot that fires a barrage of four rockets once it spots you.

Strategy
Walker 2000s are not quite as resilient as they look, but they are best engaged from a distance to give the player enough time to dodge their rockets.

Enemies still take splash damage from their own side, so a Walker's missile barrage can take out an entire squad of Grunts through friendly fire. Alerting a Walker when it hasn't fully cleared a corner is another way to exploit the AI, as it will severely damage itself from shooting the adjacent wall.