I haven't used all of them yet, but my favourite so far is Cass.

And for those wondering I'm pretty sure ED-E is pronounced "Eddie" because the quest ED-E My Love is taken from the song title "Eddie My Love" which follows the theme in the game of using song titles as quest names - so I'm fairly certain the developers intended it to be pronounced that way.

ED-E's my main man. Excellent perk and when he's not there I miss the musical warning. Seems to go missing a lot though. Boone's got a good perk, doesn't constantly talk like others, and he's deadly with the Gobi Campaign rifle. And I've got a serious crush on Veronica. Pity she likes girls (and that it's only a game).
Lily is just strange; never shuts up! Don't know why everyone likes Cass (each to their own though). She makes some funny comments, but is useless in combat. I gave her a fully modified Cowboy Repeater and she couldn't hit the side of a barn. Used up over 300 rounds in about an hour of gameplay because she starts shooting when enemies are well out of range. Maybe her and ED-E's perception perk don't work together.
I'm not sure about Raul's perk either. I gave him the Mysterious Magnum at 100% condition and within an hour or so it was worn out. He didn't even use it much; was too busy complaining about anything and everything.
Arcade is quiet (which I like) and was actually pretty deadly with the Q-35 Matter Modulator. He and Boone are probably the best shots of all the companions (imo).
As everyone else suggests Rex is useless. Having him run off all the time is annoying.

I voted for Boone, but I also keep ED-E

Since I have not used any other companion (except Rex for a quest) it is a little difficult to say he is my favorite. I am still on my first play-through so he has been my only companion.

I also don't think either Rex or ED=E count as companions, since you can have either of them (alone) with a human companion but you can not have two human companions.

Fortunately he uses it so seldom. I think it's supposed to be a take-off on Clint Eastwood.

I dont remember Clint Eastwood sound like he was eating gravel 24/7 when he talked.

I like Arcades voice and dialogue, he's such a smart alec xD

Easily Cass. Not only does she have a great personality, but she destroys anything with a riot shotgun.

I think they would have written it as E-D or E.D.

Well since i use my companions as pack mules mostly, and i find thier repetitive banter annoying after a few hours of game play i pick ED-E. Set on stay back and passive it is my own personal pack mule. Lily came in second but as most of my builds spend considerable time sneaking around the whole "grandma knows how to stay quiet" over and over again is rather annoying. Sure there is mods to shut the companions up but as i am already running 10 different mods and for the most part the only real perk that is better than ED-E's is Boone's spotter perk anyway i just use ED-E most of the time.

Asai

Boone is my favorite for a number of reasons..

1. He wears a beret!
2. Hes a sniper
3. I actually felt sorry for what happened in his quest! Made me feel connected and not like hes some stale AI following me.

Rosemary. The only companion that is stylist, charming and smart.

Veronica all the way. She's great in combat, I like her quest, her speech is great, and she's not annoying.

So far i have only used Boone and ED-E. Boone is a damn good shot, but ED-E is pretty much my glorified pack brahmin that plays music and shoots magical lazors when under attack...

ED-E is the main girl for me. She has the best perk hands down IMO and I can't help but smile when I hear Jingle Jangle whilst she is with me

Though (Cuter) Veronica in BoS Power Armour with a Ballistic Fist is a sight to behold.

I'm going to try out Cass and Arcade next time through I think.

Edit: I've used Boone too, and whilst he is a veritable killing machine, he didn't grow on me that much, plus I never got his (main) quest triggered.

My top 5 would be in this order

1. Arcade Gannon; because my brain has an orgasim every time he talks, his general knowledge of everything lets me know that I could carry on a conversation with him for hours. Also, I think he has by far the most interesting companion quest.

2. Rex; because dogs almost always make better traveling companions than people.

3. Raul; he makes me laugh.

4. Rose of Sharon Cassidy; shes just fun in general.

5. Lily; she scares the hell out of me.

I dont like Boone because hes wayyyyyy to pro NCR. "We came hear so people could live without fear" yeah, and thats why you decided to massacre Great Khan women and children and just absolutely HAD to try and claim Nevada as your own. If I was The Courier, and I was born and raised in The Mojave Wasteland, I'd be pretty pissed if some guys from California came over with hats that look like something Smokey The Bear would wear and decided that they owned the place.

Veronica is cool too, but after awhile her dialouge stops being funny and starts getting annoying.

nah bruh, boone da beast boy there lol.

Veronica. I'm playing on hardcoe, so combat effectiveness doesn't enter into my decision. If I'm anticipating combat I set my kamikaze backpack jockeys to wait as far away as I can reasonably manage. Felicia Day is hilarious and adorable. The only downside is that I feel like a right bastard every time I load her down with more repair kit mats and don't have a nice dress or some fancy lad snack cakes to give her.

Boone is http://forum.ntreev.net/grandchase/cfs-filesystemfile.ashx/__key/CommunityServer.Discussions.Components.Files/16/8838.1137775570_5F00_ffBeastboy.jpg?

Oh yeah... just what we need...

Not only is Boone overpowered already... now you want to give him Super-Hero powers!? Oi...




No, really though... I'd have a hard time choosing... but I think Veronica would win out. lisbian-Scribe-in-Exile is pretty win... although Cass is a close second. I really dug her old man, so seeing a lot of him in her is pretty awesome.

Cass! She made me laugh with her whiskey stories... And ED-E is always with me, I just love his weird battle tunes!

Boone. It seems I'm one of the few to think it on here, but I think his voice is sixy as hell I'm with Gelmir on ED-E's little battle song - it sometimes messes up my stealthy sneak, but he seems so exited, bless him.

But when you have just done a great long-distace telescopic rifle shot and he chirps up with "Let me aim that for you next time" gets reall annoying.

You're not alone. I personally love Boone's voice and I even think he's rather handsome, for a bunch of pixels. Between that & his tragic backstory, when I want to play w/a companion, I have a difficult time using anyone else. I have tried most of the others, and they're cool or cute or funny in their own ways, but Boone's got my heart & loyalty. Plus he kicks ass, even in melee, on Very Hard. I can stand idly by, maybe occasionally sticking a stimpack into his arm, & laugh at his OCD, semi-suicidal enemy hunting and no-nonsense yet slightly snarky remarks. I don't find them annoying at all. Don't really care about his Perk, just like the character & his awesome aim-bot sniping. lol

Veronica's constant "Got something for me, I bet it's something good!" or whatever it was, in that overly perky voice every time I open her inventory drove me insane. I picked her up at lvl 5 and she promptly got herself killed by trying to melee with a single pathetic bandit..eventually I told her to go home and she whined about how "everyone always tells me that." Arcade was pretty cool, I did like him/his story but he's not very nice to low-INT chrs. ED-E was charming and he's a good Perk/combat combo w/Boone. Rex was cute/sweet but talk about aggro radius, the darn mutt goes off the map chasing stuff & always into my line of sniper fire. Lily drove me insane too, even if it's not really her fault (her condition & all). The ones I haven't tried is Raul & Cass..being a gunslinger I might like Raul, but Cass hasn't intrigued me enough with her woe-is-me Caravan story to bother picking her up yet.

So most of the time I'm either solo, or it's just me & Boone, two angry snipers against the world/Legion. Hoorah.

Boone. For the personality as much as much as his ability to really hold his own in a fight. Considering I often play the chatty, intellectual character, it's usually nice to balance that out with the stoic professional who doesn't mince words. Sure his dialogue is nowhere near as colorful as Veronica's or Raul's, but he's just as deep if nor more-so. Besides, his lack of flavorful responses means that the repeated dialogue doesn't stand out as much for him --- Veronica's squealing about a dress is cute the first couple times you go to manage her inventory..... but several hours later and it's the exact same line? How about Raul's repetitive moaning about his age while sneaking?

Cass gets an honorable mention as my 2nd favorite. Great personality, great dialogue, and a lot more of it than the rest of bunch. Veronica's pretty fun, too, as is Arcade.

Least favorites are Lily and Rex hands down. The whole grandma thing was funny at first, but the only thing that'll stay attractive after an hour is her perk. All else is "DON'T YOU WORRY DEARY!! YOUR GRANDMA KNOWS HOW TO STAY QUIET!!". Rex doesn't annoy me per-say, I just don't like the cyber dog concept with the brain on full display. Plus it sounds like I've got a horse following me what with his metal legs.

Swapped them out of the team for my own Marcus companion and dog companion mods respectively. Haven't regretted it.