Panic in Classic Traveller
Classic Traveller is a great game to use for horror! And it's a very violent game so maybe you want some panic rules for firefights!
Panic
Panic can be caused by stress or horror. When a referee feels it is warranted a player must make a Panic Throw to see if they lose their cool or keep it together. Normal stressful situations require an 8+ Throw, very stressful or horrifying situations 10+, and one of a kind horrors 12+. These Throws are modified by positive and negative DMs such as: being wounded, having dealt with a similar situation, combat drugs, seeing a friend die, etc. If a player fails they must choose to Fight, Flee, or Freeze. (Referees who prefer a degree of randomness can of course map this to a d6 roll to determine randomly.)
The three physical characteristics map to the Panic Responses: Strength to Fight, Dexterity to Freeze, and Endurance to Flee. When a response is decided the relevant characteristic is doubled and the other two characteristics are reduced to 0 until the player calms down or is killed. Those who Fight do so indiscriminately trying to maintain their survival, those who Flee run away from the source of the horror as fast as they can while also shedding any gear that may slow them down, and those who Freeze cower in cover/play dead/or grovel at the source of the horror. If a player takes a wound while in Panic Response it goes immediately to the doubled characteristic. If it 0s their wounds combined with the sheer stress of the situation causes them to expire.
Example: Avery Skitnik 783553 sees an Eyeless Krongu Worm devour his crewmates. He throws a 6 against a TN10 Panic Throw. Avery chooses to fight doubling their Strength and reducing Endurance and Dexterity to 0. Their new UPP would be E00553 until they either die or deal with the source of the horror.