iPhone's Gmail app unofficially ported to Windows Phone 8
The app looks all right, but it was clearly not designed to feel like a Windows Phone app. It takes most of its design cues from the iPhone Gmail app, as well as most of its feature set. And, the early reviews are mixed, and there are some that say fetching new messages and push notifications can be slow.
Still, there aren't a lot of options for Windows Phone users, so it can't hurt to give this one a shot. The app is only available for Windows Phone 8. There is a free version and a paid version. The paid version adds push notifications, and costs 99 cents.