Wasteland 2 Beta
This page has information from the Wasteland 2 Beta and may not be accurate with the commercially available version.
Charisma (CHR): This attribute lets you know how likeable or persuasive a character is. Although it may seem like a trivial trait. it might well make the difference between life and death as you try to convince someone that you're trustworthy. Charisma also affects how an NPC will react to you when you want to hire him or trade equipment.
Source: Wasteland manual
Charisma is the combined force of a ranger's personality and desirability. People will react more favorably to a ranger with high charisma, and might talk about things they would have otherwise kept to themselves.
1-10 has a modifier to experience gained. More Charisma adds more dialog and favorable actions from NPCs.