iOS: You have lots of choices for email apps on the iPhone, but Acompli sets itself apart by offering a few features right in the app. Acompli is an email client with all the bells and whistles, along with an integrated calendar and file browser.
Acompli's main trick is the integrated calendar. At the bottom of the screen, you'll see your schedule so you can look at it at any time when you're tapping out emails. You can also create meetings right in the app and share it as a calendar invite with either Exchange or Gmail. Acompli also has a massive file browser that includes every attachment you've ever sent or received.
As for email itself, Acompli's feature-set is pretty standard. You can easily archive from the main screen, reply to emails, or dig into folders. If all you really need is email, Acompli doesn't feel like anything special, but if the integrated calendar and file manager sound appeal then it's worth a look. Acompli's free and works with Gmail and Microsoft Exchange accounts.
Acompli (Free) [iTunes App Store]