Danger Sense is one of Fallout GURPS advantages. See: Fallout GURPS.
You can't depend on it, but sometimes you get this prickly feeling right at the back of your neck, and you know something's wrong . . . If you have Danger Sense, the GM rolls once against your IQ, secretly, in any situation involving an ambush, impending disaster, or similar hazard. A successful roll means you get a warning that something's wrong. A roll of 3 or 4 means you get a little detail as to the nature of the danger.”— Steve Jackson Games GURPS sources
With the abandonment of GURPS, Danger Sense was recycled into generic combat perks.