Tremble is a devastating neurotoxin that causes uncontrollable spasms and tremors. Arguably one of the most effective poisons in the game, it causes violent shaking fits so bad that weapon use is rendered extremely difficult if not impossible. Accuracy becomes moot when one can't stop shaking, and even melee weapons suffer slowed swing rates as the unfortunate struggles with their uncooperative body to swing their weapons. In short, it causes a massive, 50-point reduction in every weapon skill the subject has (other than unarmed) for 20 seconds. It also deals 40 damage over these 20 seconds.
While tremble is the least dangerous poison in terms of damage, it is highly desirable due to its secondary effects; it can take a considerable bite out of the offensive power of virtually any human, super mutant, or ghoul foe. Note, however, that it is virtually useless on mutated wildlife, giant bugs, or feral ghouls, all of whom use unarmed attacks.
Like all venoms, it can be applied to any unarmed or melee weapon (including thrown weapons) to envenom a target on a successful hit. Note that one dose of poison lasts until the next successful strike or thrown projectile (oddly, a stack of throwing weapons remain poisoned until one of them actually hits).