The one that works great for you. yea, thats a simple answer isnt it...
That said some great ones that a lot of people seem to like are the Doge, Dark Horse, Kennedy, mad hatter...
I personally have a little boy and love it. on a 22mm mod or my box mods it is definitely my favorite. On my 26650 I have a tri-coil Atty, a Godzilla V2 and its a plain BEAST. I really like my Dark horse, massive airflow. when I drop a .15 ohm dual coil it freaking rocks. I have issues with it spitting molten juice in my mouth, but other than that it is a kick ass Atty. My Mad Hatter is a clone. and not one if the better ones. I have issues with it and use it sometimes, but its not MY go to atty.
On friday Im ordering the Twisted Messes RDA. heard a lot of good things about it, and it is just built massively. Huge wire holes,replaceable positive terminal, and looks freaking sweet as hell too.
So ther you have a simple answer, and some of my experiences. as always YMMV.