Main
* GRIM - The Curse. Raise the paranormal factor x 100!

Settlements
* Rebuilt Series Prewar Houses by rdunlap (An all-in-one package)
* Zetans Space Suit (to dress settlers for your secret lab settlement)
* Alien Encampments (to clear out alien invaders)

Other
May be compatibility issues, but worth a try.
Try PreWar Alien Invasion (Not sure about compatibility; Hasn't been tested with this mod)
Try Pip-Boy Flashlight. Uses a flashlight beam effect similar to S.T.A.L.K.E.R. and Metro 2033 adding more night suspense in X-Files lore. 
Try Take Cover by registrator2000 (Note: This mod only works on keyboard command and not PC controller.)