Have you done the storyline mission that involves going into some random mine? Then you complete the mission but if you take a wrong turn on the way out...
... I was just wandering about trying to find the exit of the mines and "heard noises", used the listening x-ray ability and there was a MASSIVE ****ing horde right above my head through a little hatch! And they heard me and started shifting and dropping down! In this tiny cramped cave mineshaft system. I spun round and legged it out of there so fast, properly **** myself, its the only time in my LIFE that I've literally screamed playing a game.
It was so satisfying going back later and setting up a load of proximity explosives then luring them out
