Game Maker:Studio is easily my favorite, but i've always been a GM person ever since the 4.3 days -- maybe the fact that i spent so much time with the tool is why i'm so comfortable with it? i will say that GM definitely has its frustrating parts, but i feel like just about every engine does, yeah? i could never get into Construct or Stencyl, and Unity is too overwhelming for my brain to handle. GM:Studio seems to be just right for me, giving me a solid set of tools while also giving me the ability to add onto it fairly easily and without learning *too* much code. (it's also a fantastic tool for prototyping!)
for pixel art, i use GraphicsGale, which is kinda like a "Photoshop Lite, for pixel art and animations" if i had to summarize it. it's about $20 or $30 from HumanBalance, but it's a great program -- albeit a little buggy in places.