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
 * Open inventory - This displays the companion's current inventory, inventory weight, and weight limit.
 * Toggle stay close/keep distance.
 * Back up.
 * Toggle aggressive/passive AI.
 * Use stimpak.
 * Toggle wait here/follow me.
 * Return to normal dialogue.

Permanent companions
You can have up to two companions, one humanoid and one non-humanoid. All companions default weapons have unlimited ammo. All companions are listed as essential on all difficulty settings except hardcore mode, where they can be killed.

Humanoid companions

 * Arcade Gannon, a member of the Followers of the Apocalypse with a mysterious past. He can be found in Old Mormon Fort.
 * Craig Boone, a very-talented 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 in 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
 * Private Halford
 * Victor

Companion lost (console/360)
Companions may sometimes disappear, while playing i lost Veronica Santangelo, but several quests later she reappeared for some reason mid-way through the quest "there stands the grass", i have recently lost the companion "ED-E" after completing the quest "guess who i saw today", and i hope he will return in the same mysterious fashion.

I've lost "ED-E" as well, but just miraculously he showed up dead in the Command Tower of Mcarran. I still have his perk and he keeps respawning to every location I fast travel.

There is a glitch when dismissing companions, no dialog option is given to have them return to The Lucky 38. The companions instead return to the original location and can be recruited later. It is unknown what triggers this glitch and no solution has been found as of yet.

Companion Lost (PC)
Lost your companion again? Told one to wait for you - and forgot him (or her - don't tell your lady companion to wait for you and then forget her, that is kinda rude) Or is your companion stuck in a cell? If you play on an Xbox or PS you are out of luck. If you play on the PC on the other hand, basically this is all you have to do:

for ref_id have a look at the companions page on this wiki, the last row of their Character-Box usually states their ref-ID.

To get the console up and running have a look at the Console Commands

You can use (instead of both commands stated above) too - if you want to know where you lost your companion and feel lucky. In other words: save the game before you do this - it might save you some frustration.