GDBFrontend
GDBFrontend is an easy, flexible and extensible gui debugger
...Expressions of all variables, members, and items are connected in GDBFrontend's VariablesExplorer. You can watch, filter or manage processes with Process Manager. GDBFrontend has a set of features for collabration named as "Enhanced Collabration". Collabration draw is available when you enable Enhanced Collabration. Click to Draw or use Ctrl + Shift + X shortcut to draw and Ctrl + Shift + C to clear all drawings. With Enhanced Collabration all debugger clients are synchronized on source viewing. GDBFrontend is very extensible and has powerful APIs. Some examples of GDBFrontend's extensibility.