Charisma

Charisma naturally improves non-hostile characters' reaction towards you so they will give you better prices and generally be more agreeable. Charisma abilities will often unlock more options in dialogue, or let you recruit more teammates. -the players manual
(5) Detect Motive: Informs you of your target's faction, and possibly other information for important characters. This also functions as a passive ability, allowing for new options in dialogue.
(10) Negotiator: This ability gets you bigger rewards for accomplishing jobs. This is a passive ability, allowing for new options in dialogue.
(10) Motivational Speech: You can motivate a teammate with a few positive words and a confident smile. Target somebody on your team and that person will receive a temporary +10 to Agility, Strength, Pistols, and Rifles. The amount increases with a higher Charisma skill.
(15) La Mordida: La Mordida, the Bite, is a local word meaning "bribe". Pay 50 jink to any member of a non-hostile faction to raise the respect of that faction by 3%. The respect increases more with a higher Charisma skill. This ability is useful for bribing people who saw you steal something.
(20) Man's Best Friend: You have an affinity for animals. You can charm a hound to follow you and fight for you with a piece of meat. With 20 Charisma skill, you can even charm hostile hounds. The hound will join the team, but you cannot directly control it.
(30) Lady's Man: Pay 60 jink to a hooker to acquire her protection services. She will join your team, follow you to new areas, and stay with you until she dies or is dismissed. With 40 Charisma skill, the price decreases. This also functions as a passive ability, allowing for new options in dialogue.
40) Recruit Soldiers: Pay 100 jink to a friendly UB Merc, Thug, or Scav Ghoul to make him join your party. Pay 200 jink to a friendly UB Elite or Juicer. The character will join your team, follow you to new areas and stay with you until he dies or is dismissed.
(50) Born Leader: You can have one extra character on your team, for a total of 4 (including your main character). It also opens up new options in dialogue. This is a passive ability.
(all of these descriptions are from the players manual)