Fallout: New Vegas companions

Companion wheel
The companion wheel is a new feature that is added to Fallout: New Vegas. The wheel provides easier control over non-player companion characters in the game.

There are 8 sections on the wheel, each with a specified function.

The available orders are:
 * Toggle melee/ranged fighting - also displays weapon being used. Also if you instruct a companion to change their combat style they will make a comment hinting towards the best combat style for them.
 * Open inventory - This displays the companion's current inventory, inventory weight, and weight limit.
 * Toggle stay close/keep distance.
 * Back up-makes them back up a few yards.
 * Toggle aggressive/passive AI.aggressive-attack enemy on sight, passive-only attack when you attack. helps when sneaking around places you have a lot of enemys in.
 * Use stimpak - also shows current health.
 * Toggle wait here/follow me.
 * Return to normal dialogue.

Nerve
Each companion also has a special attribute referred to in the game as Nerve. Nerve affects a companions combat effectivness significantly and can only be increased by increasing your Charisma.

Permanent companions
You can have up to two companions, one humanoid and one non-humanoid. All companions default weapons have unlimited ammo. If you equip your follower with a better weapon add ammunition and check its count from time to time - they seem to hold on to the new weapon when out of ammo and switch to melee instead.

While actively following you, permanent companions are treated as essential (unless you are playing on Hardcore Mode, see below). It is important to note that they are only essential when following you, and they can be killed both before they join you and after you tell them to leave. In Hardcore Mode, companions can be killed even while actively following you, but they do not require food or drink, and are not affected by radiation.

Should you tell your companion to wait for you at The Lucky 38 they will be waiting in your presidential suite ready to be rehired.

Humanoid companions

 * Arcade Gannon, a member of the Followers of the Apocalypse with a mysterious past. He can be found in the Old Mormon Fort.
 * Craig Boone, an Ex-NCR sniper with a grudge against Caesar's Legion. He can be found in Novac.
 * Lily Bowen, a friendly nightkin and former member of the Master's army. She can be found in Jacobstown.
 * Raul Tejada, a ghoul mechanic and former gunslinger held hostage by Tabitha, the mad leader of the State of Utobitha. He can be found in Black Mountain.
 * Rose of Sharon Cassidy, a caravan merchant and the daughter of John Cassidy. Also known as Cass. She can be found in Mojave Outpost.
 * Veronica Santangelo, a disillusioned Brotherhood Scribe. She can be found at 188 Trading Post.

Non-Humanoid companions

 * ED-E a prototype eyebot designed for combat and reconnaissance operations. It can be found in Primm.
 * Rex, a cyberdog belonging to The King. It can be found in The King's School of Impersonation.

Temporary companions

 * Neil, a disgruntled super mutant.
 * Sunny Smiles
 * Trudi
 * Deputy Beagle
 * Securitron Mk II (Or Securitron Mk I)
 * Private Halford
 * Victor
 * NCR Ranger (activated via NCR Emergency Radio)
 * NCR Trooper (activated via NCR Emergency Radio)

Returning Lost Companions (PC)
Push the Tilde key and then type in.

The Ref id's for companions are listed on their respective pages.

You can use (instead of both commands stated above) too - if you want to know where you lost your companion. Be sure to make a new save before using any Console Commands.

Sometimes a companion will disappear and not seem to be retrievable by fast travel or the moveto command.

In that case, attempt this:

Move all items from the targeted companion over to yourself to avoid losing them.

See Console Commands for more information on how to use the console.

Bugs

 * Bringing companions that have weapons into Casinos and other places that remove the players weapons will sometimes remove the companions weapon also, putting it in the players inventory. If dropped on the ground -- it will say "Steal" or "Take" with no weapon name shown, and you cannot pick it back up and your companion can only use your weapons with ammo supplied with it. This is somewhat common, and can be extremely problematic since the fix for this has not yet been discovered (if there is any).
 * Note: Rex and Ed-E are safe, as they don't use actual items for weapons.
 * If you choose to upgrade Ed-E's armor or weapon by leaving him with either faction upon completion of Ed-E's mission, be sure to take all of his inventory before you do, as he will have lost it once he returns to you (confirmed on PC Xbox 360 and PS3).
 * I got the achievement for having all companions without getting Veronica, I do not know if it is relvant but ED-E and Boone were my companions at the time and the last companion I got was Arcade Gannon.