Tag!

Tag! is a Fallout, Fallout 2, Fallout 3, J.E. Sawyer's Fallout Role-Playing Game and Fallout Tactics Perk.

Fallout, Fallout 2 and Fallout Tactics
Your skills have improved to the point where you can pick an additional Tag Skill, increasing that skill by +20% immediately and 2% per skill point spent.

Fallout 3
The Tag! perk allows you to select a fourth Skill to be a Tag skill, which instantly raises it by 15 points. Because of the reduced properties of tag skills, this is essentially nothing more than a 15 point bonus to any given skill.