Which THREE DA2 companions are must-have for you?

I missed the survey, but here are my choices:

Aveline, Merrill, and Bethany.

I have no absolute:
Most of the time Varric, Aveline, Merrill, classic.(skills/romance)
I switch them depending of the situation : Merrill/Anders(coz I like him), & Aveline/Isabella - like her delicious impertinence
Sebastian & Fenris are real pain at some points : they showed a lack of tolerance.(which could be a thread subject)
I regret Talis couldn't become a principal partner, it makes her more precious.

Varric (way OP), Anders (excellent defender, decent healer) and Fenris (always kills everything before me lol)!

Varric, Aveline, and Merrill.

Aveline, Anders and Varric (The strawberry blonde crew...)

Can I just vote for Varric*3?

I actually like the DA2 cast. Assuming a mage run:

Varric, because no one replaces my BFF, ever.

Aveline, because she's a beast. And her + Varric = comedy gold.

Bela, because she's my preferred romance option.

That said, long as Varric's around, the rest could go or stay.

Can't vote now, but I agree with Varric being a favorite. Numbers 2 and 3, Anders and Fenris, however, are at the bottom of my list. For my mage, Merrill or Bethany (when possible), and Aveline ends up being my tank. I also like Isabela.

That sounds like my kind of party.   Isabela is my favorite too, becuase I honestly thought that both Anders and Fenris had something wrong with them, and i ended up leaving them both for Isabela.. 

So far im loving Varric, Merrill and Aveline in a group and my mage Hawke of course

Varric and Anders are musthaves for me. As the third companion, I would probably go with Aveline.
The reasons: I love those characters the most from all companions and they are the most useful imo. Isabella and Fenris aren't bad too, but I just like Varric and Aveline more.

Merill, Varric, and Fenris. Curse your sexy, sexy voice Fenris. I feel that in the same vein as "Stupid sexy Flanders!" Not interested but, gosh darn it, take your sexy voice somewhere else Fenris!!

No contest whatsoever.

Aveline
Isabela
Merril

Aveline is an essential tank, and no other companion (unless modded) can match her ability to soak up damage and round up foes. Isabela, if specced for pure damage, is like a human buzz saw capable of ripping apart anything in her path in nanoseconds. With Haste, the right gear, and critical strike synergy from other companions' auras etc, along with high defense from cunning, she's unstoppable.

Merril is a great utility/support companion who doesn't need mana, and provides excellent AOE damage. I'll typically team up with a Mage Hawke, so healing is no problem - besides which I use a mod that unlocks all companion class trees, even ones they're not supposed to have, and lets them use any weapon - so the game feels far more like Origins. Therefore my version of Merril also has a healing spell even if she can't use it on herself unless she removes all her sustained abilities.

This team, coupled with a Mage Hawke can handle almost anything the game throws at them, and has the flexibility to cope with most situations. Only foes with deadly AOE effects such as elite-level Arcane Horrors give the team pause, and in those cases, I'll equip Bela with a bow for the duration of the fight.

Additionally I like the dynamics of the banter between this team. Avelines' gradually-growing respect for Isabela is particularly nice to see, and Isabela and Merrils conversations are often hilarious.

I'll also make use of Varric fairly often when Isabela needs a break, or he's compulsory (Deep Roads and Legacy), and Fenris now and again, but Anders and Sebastian will generally start to rust from disuse.