We use git and wiki, along with code review tools on assembla.

Tasks are easy to create and assign. Time is easy to track. Assembla is a less frustrating tool to work with compared to similar products. I've recommended Assembla for small teams of 2 people, to larger teams upward of 20. I'm sure it scales well for even bigger teams. There are many tools that connect well together, like referencing tickets in your messages. It makes it easy to organize the entire space.

Being able to use perforce in the cloud and have all the of the server management handled by someone else helps keep us focused on developing our game and not worried about version control or backups.