I use Snapseed on Android. It's a practical app with many photo editing tools
I like how I can edit my photos here,
Pixlr - Pixlr® makes it easy to transform everyday images into stunning works of art.
VSCO - VSCO® is an art and technology company empowering people everywhere to create, discover, and connect. CompanyVSCO® is a trendsetting art and technology company that .
Adobe Photoshop Express - Easily edit and share your photos in no time!
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
PicsArt - Explore 100,000,000+ awesome images and photos on the web
Pixlr-o-matic - Add retro effects to your photos in a snap!