iOS: Dispatch is one of the best email apps for iOS, especially for power-users. Today, it gets a bit better with a new iPad version alongside some new actions and snippets.
The big news is the iPad app, which is included if you've already purchased Dispatch. Like most email apps, the iPad version has a list of messages on the left with the selected message on the right, but also includes a handy set of shortcuts.
You can also dock messages so you can easily reply and manage emails in bulk. Beyond that, both versions of the app get the ability to sort actions and new auto-suggestions for snippets you might want to use.
Dispatch ($8.99) [iTunes App Store]