I'm surprised I haven't posted about soapUI yet given how often I use it. It's one of the first web service testing tools I ever used, and I haven't had much need to look elsewhere. soapUI is great for both functional testing and performance testing. They also have a great service mocking feature.

I've never used the pro version, so I can't speak to those features or the support that comes with it. But I will tell you this, the first (and only) time I had an issue with the tool I contacted the developers and they had a build for me the next day with a fix. I was amazed at the turnaround. I'm sure not all fixes can happen that fast, but it still says something about their passion for the tool and the people that use it.

You can checkout the full feature set here: