I use SpeedCrunchas my default calculator. I use 0.11-alpha because the release version was missing some important feature--though I can't recall what that was.
-It's like a hybrid of the Windows built-in calculator and the PowerToys calculator.
-Sessions can be saved
-Works on latest versions of Windows
-Hasn't crashed on me
-No graphing support
-Hasn't been updated for years
-Limited binary support (No binary operations, but you can view the results as binary.)