In my previous organization I used HCL AppScan for a brief period of time, and I started using AppSpider instead when I moved over to my new organization. Comparing the two, I don't see many differences in terms of functionality. Another web app scanner I used recently is called Yaazhini.

Although I haven't used it yet, I have also heard good things about Checkmarx.

I have used Nessus in the past, and the performance of Rapid7 is better.

We did use a different solution, but we wanted to try this product and so far we really like it.

I have tried a couple of open source solutions like Burp Suite but nothing that is in competition with AppSpider.