Salesforce and I can't believe more integrators aren't using it. Its a very basic CRM out of the box and does require development, but its probably one of the most customizable platforms available. We can do virtually anything we want or need and the programming is moving to all GUI based programming. Truly incredible.
Salesforce does the work of nearly 3 full time staff for us and brings us incredible ROI. We are on a huge push to reduce swivel chair and live entirely in Salesforce ecosystem.
The only negative I have on Salesforce is that there is talks about Google acquiring them, and those transactions are often a little bumpy.
Oh, and Salesforce puts on a Dreamforce conference every year which is not only a blast, but incredibly powerful to understand whats new and how to further create automation, efficiency and magic :)