I use Aseprite for most of my work, mainly because I like the UI. It was very easy for me to learn and many tutorials exist for it. The only thing I don't use it for is tileset work, but they just added tilemap functionality in the 1.3 beta. I currently use Pyxel Edit for all of my tiling needs, but it is also a good all around spriting application. Recently, I also started using Pixel Studio, a free pixel art editor with a mobile app and Google Drive functionality, so I can sprite on the go. I'm still learning the shortcuts and UI, but it is a very well made editor.