I use GIMP, mostly.
I love that it's open source and free, but of course that comes with some drawbacks. I've learned to work around most of them now. I wish I had a better set-up for animating, although I probably couldn't make use of one very well if I did anyway.
I'm not really sure how to describe my style, but its 2D and I suppose it's quite messy and low-tech. I have to work quite small because my laptop/GIMP can't handle big files, but I'm also not very careful and I don't use a restricted palette usually, so it doesn't look like pixel art although it's often small enough to see individual pixels.
I have tried sprite lamp for dynamic lighting, but I didn't like the look of it in my style. I probably need more practice with it.