What is a good app for editing photos?

What is a good app for editing photos?

Lensical:

Platform: iOS (iPhone)
Developer: Apptly, LLC
Price: Free

Lensical makes creating face effects as simple as adding photo filters. Lensical is designed for larger displays and utilises one-handed gesture-based controls making it the perfect complement to the iPhone 6 and iPhone 6 Plus's cameras.

Photo editor

Photoshop.

Adobe Photoshop.
The very best.

Depends, I would only recommend Gimp or Photoshop. Photoshop costs lots and I don't consider it worth it cause though it looks better and has a better setup you can do all the same stuff for free on gimp.

If you have a Flickr Account and only want to do basic editing, you can do it within Flickr.

Photoshop CS6 Extended does it for me.

VSCO Cam (iPhone, Android)
Snapseed (iPhone, iPad, Android)
Adobe Lightroom (iPad)
Instagram (iPhone, Android, Windows Phone)
Flickr (iPhone, Android, Windows Phone)
Photo Studio (BlackBerry 10, Android)