Project Management Software

We all know that we have to pick the right tool for the right job but do we as Project Managers really know what software best fits our current needs? I know for sure it is not always the software the clients has and I know it is not the most expensive or free-ware on the market. Most of the software out there like MS Project can do the job but it is our experience and knowledge that really makes or breaks a good plan. I would like to hear about the kind of PM software people are using with success (+/- 28%).