The Fast App Switcher is a third-party Small App for Sony Xperia devices. Development of the app has been progressing over at XDA for the last couple of months, but now version 2.0.0 is available to download on the Google Play Store.
The Small App allows you to keep the app switcher at the foreground, maximising your productivity especially if you are constantly switching between apps. There are a ton of customisation options including adjusting the number of viewable apps, pinning the Small App, the ability to choose a horizontal or vertical layout and a context menu for each app.
The app is available via the Play Store along with a Pro version to support the developer for €1.00/£0.59. The Pro version allows you to load the Fast App Switcher at startup and you can choose a favourite apps list or even tag other Sony Small Apps as favourite apps.