There are many Brony artist on deviantART, but one of my personal favorite is devilkais from Tunisia.
What makes him one of my favorite Brony artist is his style of drawing, which is Looney Toones / Chuch Jones style animation. I admire that he enjoys this style while going into the grimdark side of the MLP universe and other universes (DC, Marvel, Disney, and Looney Toones) although he does not like Princess Molestia or Megasweet's child XXX of the CMC.
I personally enjoy his drawings of Spike, who is more reptilian than he is on the show.
His favorite members of the mane six are Rarity and Pinkie Pie.
Derpy is his favorite non mane six pony.
Here are some of his MLP drawings: