For me it will be Farkas, the guy never gets in my way and is a life saver.

I personally love Lydia, although enemies are starting to get harder and Lydia never levels up. Time for a new follower, I should think!
Jenassa is always a good fighter, too.

I don't really have a specific preference, but I suppose I prefer archers because they stay out of the way. I swap out companions all the time, though. Fire one to go solo for a while then if I feel I may need some extra muscle I grab whoever is closest.

Stenvar Im a heavy knight hes a heavy knight and hes a mercenary followers dont level up but mercs do. Plus they only level up in the things that you level up in hence why I picked a heavy knight. He has few good lines to such as if my mar could see me now she would scold me good.

GO TEAM KHARJO!!!!!!!!!!!
But I also like Janessa, Aela, and J'zarrgo. Kharjo has been with my khajiit from almost day one and has pulled my a$$ out of the fire tooOOOoo many times to count, I did recently promote Kharjo by using the wabbajack on em and now he is an ubber tank, lots of fun playing " who can kill the bandit first"

Depends on my character. My evil mage is using Jenassa, but will switch to Cicero when I get him, My assassin chick used Eola for a long while, but has recently switched to Lydia (so they can be two crazy chicks [censored] stuff up in Skyrim), My politician uses Jordis his humble Sword Maiden as a bodyguard, housecarls are a little boring but they're helpful. My Khajiit travels with other beast-races, and generally uses Kharjo or Derkeethus, but sometimes he'll take the wife Mjoll out until I realize she's permanently overencumbered and can't carry anything anymore.

Erik the Slayer for me. He's a great tank and has done really well at staying out of my mage's way. He sets 'em up, Eira knocks 'em down. They make for an awesome duo. He's not the sneakiest companion in the world but he actually does surprisingly well for a tank--I've been able to sneak past a couple Forsworn encampments with him in tow. Somehow he's learned to avoid setting off traps, too...or at least only hurting himself when he does set them off.

He does have an odd obsession with finding every single fire-based pressure plate in a dungeon and standing on it until it nearly crispifies him, though. Not sure what that one's about. (I am not even joking about that, btw. We can be in a wide open space in a barrow and he'll find the one pressure plate in the middle of it and immediately go stand on it. And then be upset that's he's somehow caught fire. )

I like the Khajiit and the Argonian.

I hope I can get Faendal, I haven't checked wether or not I did the quest I dont remember but he fits perfectly stat wise with my own character, if he doesn't work it will be a choice between Marcurio or Jenassa. How sneaky are the two?

My favorite is Kharjo, my loyal and obedient housecat! The problem with him is that once you let him go, you'll never know where to find him as he travels with a caravan.

The orcs.

Depends on the character i'm playing. but Faendal and Erik The Slayer.

My wife, Janessa.
She fits perfectly with my sneaky guerilla type Dunmer dual wielder.
She's one of the only followers who will DW.

Dremoralords...

I prefer Brelyna, Onmund or J'zargo

I use my own companion from the CK. His name's Bob and he has no standard inventory. I gave Bob a torch and he wears Daedric armor.

Why did I do that? Every f'ing follower hits me more often than the enemy, they are actually reta*ded, I hate them all. And I like to think that the mighty Dovahkiin Valtyr Stormblade clears caves full of Draugr with his loyal friend Bob. And he can't kill me with the torch but so I can see stuff without carrying it myself.

I go solo most of the time, but I prefer Derkeethus and Aela.

Marcurio.

Always Marcurio.

This guy always knocks into me and killed me more than 3x. He knocked me into a trap and woke a dragon priest up, when i SPECIFICALLY told him to wait at a far away place while i go ninja mode. I ended up kiling him and leaving his body in riften market naked.
Best companion? One that does not die easily and know how to avoid traps, like jenessa.

I had Brelyna die while fighting a powerful Draugr in the last College of Winterhold dungeon ... So I've decided not to risk any more apprentices!

If you use the wabbajack on her (dismiss her first) until she transforms into a chicken/daedra/mud crab, then punch her she will transform back scaled to your level. This will reset her equipment though, she will also come back non-aggressive if you pissed her off before.

I know, but I haven't done any Daedric Quests with this character yet so it isn't really an option.

Ah fair enough, you can also dismiss her then leave the cell and wait for a few days. People say the time is 30 days, but she has reset for me in much shorter time periods.

As far as daedric quests go, the wabbajack one isn't evil or morally questionable, you just do a number of weird tasks for the daedric god of madness (who is rather crazy, as you'd expect ha).

The only part of that I don't understand is the scale to you part. Does that mean that your companion is leveled to you(like if your Lv.81 does the follower level to 81) or that your companion reaches the companion cap of 56 or what ever the cap is for companions?

Some companions level to 30, some to 40, some to 50 and two (j'zargo and dark brotherhood initiate) level right up to 81. Look on the uesp website on the followers skyrim page, scroll to the bottem and there is a link to all the followers and their levels.