There are very few modern use cases where WCF is the best option out there. If you want to make a RESTful API with .NET, please consider:
* ASP.NET MVC Web API
* ServiceStack
* Nancy
Nancy is basically Ruby's Sinatra but then on .NET.ServiceStack recently became commercial, but it still is the best designed API library I've ever seen, in any language. It makes you focus more on the actual data inside each request and response, and less on the form of that data (is it a query parameter, JSON POST field, or part of a fancy URL? who cares, design your messages first and then figure out what the URLs should look like). The result of this is that somehow you tend to automatically design forward-compatible, extensible API endpoints. I guess you really have to feel it to believe it, but I kid you not, with ServiceStack, it feels like your API designs itself in front of your eyes.
If anyone knows anything like ServiceStack on any other language, please tell me and I'm going to give you hugs.
Finally, MVC Web API is basically Rails's API controllers ported to C#. It has a tad too much magic for my taste, but it's a familiar and decent pattern that just works.
Please, please, let's just bury WCF and embrace the true goodies in the .NET open source ecosystem. It's nice that WCF got open sourced, but it's still a mess. If you really must go the "because Microsoft!" route, please just use ASP.NET MVC (also open source, and in active development).