On devices with Camera2 API support (currently LG G4, Nexus 5, Nexus 6, Samsung Galaxy S6/S6 Edge), ProShot offers full manual control over ISO, shutter, white balance, and focus, in any mode, even during video recording.
ProShot has options for 4:3, 16:9 and 1:1 aspect ratios allowing the shooter to choose what best suits their intended shape. It also has support for custom aspect ratios, so 3:2, 21:9, 50:3, and more are all possible.
ProShot requires that the Android OS is on version 5.1 or higher in order to install and work. Considering there is only a developer preview for this version to date, it basically can not yet be installed. Even when 5.1 comes out there will not be many devices using it.
Developer's note: there are many camera bugs in 5.0 that are only fixed in 5.1. Support for 5.0 may come in the near future, with some features locked until the upgrade to 5.1.
This app boasts over 100 filters. In addition to these filters, additional settings show up for each filter. For instance, HDR mode has 4 different settings in order to be situation appropriate. Each filters's intensity can be adjusted on a scale of 0 to 100.
Using the Audio mode, 5 seconds of sound are captured with the image to "capture the moment". It's hard to tell how this could actually be useful, but it's a cool feature.