Did you know that there are eight individuals across the Mojave Wasteland? When you find a follower, and ask them to join you, you get a unique perk. Each Character gives you something different. Not only can you have one follower, but you can also hire mercs, which will allow you to have up to five in your party.
Here is a list of the companions with locations and perks.
Robot Companions:
ED-E:
Ed-E is a prototype eyebot with repressed memories.
Location: Primm
Perk: Enhanced Sensors
Quest: Ed-E my love
Upgrade: ( need to complete quest) Enhanced Armor, or Enhanced Weapon.
Advantage: Ed-E is awesome at detecting enemies early, and is best fitted as a ranged support role.
He is best paired with boone, but also does well, with an unarmed follower. I.E Lily
REX:
Rex is The King's best friend, he is loyal, but has a broken brain.
Location: The King's School for Impersonation
Perk: Search and Mark
Quest: Nothing but a Hound dog.
Upgrade: ( need to complete quest) New Brain (Enhanced Strength, Toughness, or Speed)
Advantage: Rex is quick and inflicts melee damage with a knockdown effect.
He is best paired with a ranged companion as in boone, by keep foes busy with melee.
Humanoid Companions:
Arcade Israel Gannon:
Israel is follower of peace from a tribe devastated by war.
Location: Old Mormon Fort
Perk: Better Healing
Quest: For Auld Lang Syne
Upgrade: (need to complete quest) Hoover Dam help, or Tesla Armor (gift)
Advantage: He is the weakest human, so keep him at long range support with a energy weapons, and get better armor for him as possible. He provides good support for combat characters with his perk and does a good amount of ranged damage.
Craig Boone:
He has lost his wife, but not his guilt or rage.
Location: Novac
Perk: Spotter
Quest: One for my baby, and I forgot to remember to forget.
Upgrade: ( after 1st quest) 1st Recon Beret. ( + perception, +5% critical chance)
Upgrade: ( after 2nd quest) 1st Recon survival armor, or 1st Recon assault armor. (cosmetic difference only)
Advantage: He is a ranged specialist, and deals a high amount of damage as long as enemies are not to close. Best used against Cazadors, and radscorpions. Try sniping at night, with the spotter perk, enemies are visible in the dark. He is best partnered with Ed-E, so you can defeat enemies sooner.
Rose of Sharon Cassidy aka Cass:
She has a chip on her shoulder and a thorn in her side.
Location: Mojave Outpost.
Perk: Whiskey Rose
Quest: Heartache by the number.
Upgrades: Hand of vengeance (upgrade to guns) or Calm Heart (bonus to health)
Advantage: Well rounded, but does not do armor piercing damage, unless you upgrade her weapons. Best used as ranged but holds her own as a melee fighter. Partner her with another Melee character or Rex.
Lily:
The Super Mutant Grandmother, very overprotective of little timmy.
Location: Jacobstown
Perk: Stealthgirl
Quest: Guess who I saw today
Upgrade: ( need to complete quest) administer medicine to affect psychotic breaks and combat damage.
Advantage: She is a tank, and deals heavy melee damage, but also fires well at range. Pair her up with rex and Israel to do make an awesome team.
Raul Tejada:
Dry Humor, drier skin, but a flood of old memories.
Location: Black Mountain
Perk: Regular Maintenance
Quest: Old School Ghoul
Upgrade: (need to complete quest) Vaquero (increased weapon ability ) or full maintenance ( Perk Upgrade)
Advantage: Raul offers a repair service at his shack, his perk provides great counter-balance to the built to destroy trait. When you are not repairing, he is best to hang him in the back, he will not wear any heavy armor.
Veronica:
BOS, Happy to be out of the bunker.
Location: 188 Trading post
Perk: Scribe Assistant
Quest: I could make you care
Upgrade: ( need to complete quest) Power Armor or increased damage with her Power fist.
Advantage: Best on melee, should partner with her early on, she can take on the legion with ease.
She is an awesome companion for energy weapons characters as with the vigilant recycler perk you can convert zero weight spent energy cells into ammo on the fly with her repair bench ability.
Hope this helps you survive the Mojave Wasteland!!