One Hander

One Hander (called Unidextrous in TORN) is a Fallout, Fallout 2, Fallout Tactics, Lionheart and TORN Trait.

Fallout, Fallout 2, Fallout Tactics
One of your hands is very dominant. You excel with single-handed weapons, but two-handed weapons cause a problem.

You have -40% to hit with two-handed weapons, and +20% to hit with weapons that only require one hand.

J.E. Sawyer's Fallout RPG
You excel with one hand, but two-handed weapons cause a problem. +2 chance to hit with one-handed weapons, -2 to hit with two-handed weapons.

Lionheart
You suffer an initial -10 to Two-Handed Weapon skill and -10 to Ranged Weapon skill but obtain a +10 to One-Handed Weapon Skill.

TORN
The character is +20% to-hit with one-handed weapons, but -40% to-hit with two-handed weapons and suffers an additional -40% to-hit penalty when dual-wielding.