Ready for Action! Achievement in Doom 3: BFG Edition
Ready for Action!10
Get the BFG-9000 from Security Chief's office in DOOM 3
How to unlock Ready for Action!
At one point in the Delta Labs chain of levels, you will come to a section where you must use yellow boxes and a crane to reach a ventilation shaft on the wall above you to the right.
Get up there, then go through the shaft and drop down. Turn around and then look in front of you to the left. You will see an office room with the BFG-9000 inside. Input the code 931 on the door panel and there you have it.