Ghoul Ecology

Ghoul Ecology is a perk added to Fallout 3 in the Point Lookout add-on. All your weapons do an additional 5 damage against ghouls.

Obtaining
The perk is gained by reading Plik's journal inside the Coastal Grotto.

Note
While the description above indicates that all of your weapons do an additional 5 damage against ghouls, the help text for the perk itself (shown on the right) simply says "+5 damage against ghouls." Unverified whether this perk inflicts bonus damage only with weapons, or also with unarmed attacks.