Title says it all 
Goldius(not out yet tho, I just know it will be). 
This is a toughie. It’s a four way tie between Breezeling, Sanders, Ventowyrm, and Cyrowyrm.
Maybe the first two will raise some eyebrows, so let me explain myself. Yeah, they’re cute, and yeah, I like birds, but that’s only part of the reason why I like them.
Breezeling, aside from being ridiculously adorable and having an awesome design, is actually pretty good for such a common ark. I have a fondness for quick arkadions/creatures, and it just so happens breezeling was a bird, looked cool, and was decently speedy. I’m currently playing on a save file that has a team composed of only breezelings, breezekites, and breezehawks… and I’m doing fine so far. It’s fun and challenging!
Sanders… well, Sanders is cute too. But Sanders was also one of my first arks, and believe me when I say I was angry when I saw it only had 5 hp at lvl 1 (I think). But it also has stun skin, and once it evolves into Kentucky, it’s actually a pretty good arkadion. It gains a lot of HP too, haha, and it’s a chicken, so of course I’d like it.
Ventowyrm, although having the same stats as the other dragons, just looks cooler to me. I also always go for the air element, or sometimes the water element. I never go for the earth element and only rarely the fire element. So ventowyrm… well, it’s a natural choice for me. Not to mention the vengeance. I love that skill.
Cyrowyrm is the best 12* out there in my opinion. To quote Ashley:
I’m definitely not a strategist. And I like huge damage. Thus Cyrowyrm is for me.
What about you, Squirrelgirl? Seedtooth/Leaftooth/Shrubtooth? Those were my best arks up until the middle game, maybe even late game. But they were pretty awesome, and I was lucky enough to find an S grade at first. My Shrubtooth and Skullwraith were unbeatable!.. but I can’t say the same for PvP. <<
Vegitiger- a vegetarian green striped mass destruction tiger… Nuff said
My favourite are Halopard or Angelon. Just because they can be used as support arks, or attack arks.
Halopard more than Angelon because of reinforce.
Hmmm, right now i really like the scorpion its deadly in some cases…
also snowja -> no Guard ’ xeno - ba - metal slash…
or twigster it has firenull gives it self 100% protect from fire til its hit. and ofc last stand and last Will … Charisma and retreat:)
Stego because it makes pvp really fun being permanent stunned
My favourite is… Scorpionix
Plasmorex because it looks awesome!
Donstun avatar Ark.
Thought your favorite was Charcalynx or Stego. 
Not out yet but mine will be cyberwyrm.
Stasis, timestrike and really good stats. Probably the best wind ark in my opinion other than triphoon
It’s tough for me to say, as I have not gotten to know them all yet. Seedtooth/Leaftooth/Shrubtooth are definitely up there in cuteness ^^ but usefulness is another story, and I’m typically a big fan of pvp, so we’ll see once I know them all!
Shadowstalker.Â
+1
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Because it is perhaps the most versatile ark, and its a tiger.
Close second would be Scorpionox, because of color scheme and power.
halopard i have played thru the story line 3 different times and everytime i use the first egg i get halocat and halopard is always an efficient helper 
Vortexor: AoE banish is not to be underestimated.
Runner Up: Kamiwurm. love hate relationship here. I really want to get this ark but I’m not sure if I’ll play as often on e I do get it. So I am enjoying not having it… If that makes ant sense.
I like FROSTKIT!!! And ss, and meowzard, and felimancer, and halopard, and that Pharaoh cat (even though its really weak). Yup. I bet you could never guess what they all have in common
^they all have a vowel XD
I’m so smart 