Alcantarea

Alcantarea is an add-in for Visual Studio that allow you to apply C++ code changes to running programs. This functionality makes development iteration cycle drastically faster, and makes C++ programming more fun.

Visual Studio has similar functionality called Edit and Continue. Alcantarea has some advantages and disadvantages.
Notable advantages:

• Alcantarea supports x64 native code
• Alcantarea works with optimized code (/ZI option is not required)

Notable disadvantages:

• Source code debugging will not work after applying changes
• Alcantarea does not support managed code

Although these disadvantages are serious, these advantages are very helpful especially for game developers.

more info: http://primitive-games.jp/alcantarea/