Snapseed recently updated to version 2.7 on the iPhone. It is generally my 'go to' application for quickly adding some pop to photographs on the iPhone. It has a nice clean minimalist interface thats intuitive and can easily share photographs to other applications on the phone (think Instagram). The update came with a really nice new feature though, it has added a section called "Insights".
The insights feature provides short tutorials on how to add different effects using the application. It also has photographer interviews, which are really good for finding out about how they got into the business. The insights feature is a nice addition if you need some inspiration.
The photograph I have added shows the "Detailed Black and White" insight, added onto a photograph I recently took of Edinburgh Castle. It's a bit more 'effect' than I would apply, depending on my mood of course.