Let's face it, with the built-in editors and apps like Instagram and Flickr, it may seem strange that my favourite Android Photo editing app is Vignette, but let me share with you two words - Full Resolution.
Other apps may be more popular, but the paid version of Vignette offers photo editing without a compromise towards image quality and size. To put it simply, Vignette doesn't make your photos smaller.
This is the paid version of the Android app, and to date it's the only application I've paid for, but it's worth every penny. There are a wide variety of filters, from lomo type extremes to subtle black and white or colour conversions.
There's some nice frames as well, and the only missing feature is the ability to straighten images where they're slightly off kilter, but I'm sure we'll see this in an update in the not too distant future.
So, if you want the best photo eding app for your Google Android Smart-phone, like my Samsung Galaxy Nexus, head on over to the Play store and grab Vignette, you won't regret it.