These are the WPF tools that I know about and use on a periodic basis:

Free Tools:

• Kaxaml
  

  Kaxaml is a lightweight XAML editor that gives you a “split view” so you can see both your XAML and your rendered content (kind of like XamlPad but without the gigabyte of SDK).Kaxaml is designed to be “notepad for XAML.”

  It’s supposed to be simple and lightweight and make it easy to just try something out.

  It also has some basic support for intellisense and some fun plugins (including one for snippets, one for cleaning up your XAML and for rendering your XAML to an image).

• Pistachio
  

  Pistachio is a utility I created with fellow Infragistics VDGer Tim Hussey. It’s pretty simple really, you just open a .csproj file with Pistachio and it identifies all resources defined within the project, then shows you which of those resources are used and where they’re used.

• Snoop
  

  “Snoop … the WPF utility by Pete Blois and now maintained by Cory Plotts that allows you to spy/browse the visual tree and change properties … amongst other things.

• WPF Inspector
  

  WPF Inspector is a utility that attaches to a running WPF application to troubleshoot common problems with layouting, databinding or styling. WPF Inspector allows you to explore a live view of the logical- and visual tree, read and edit property values of elements, watch the data context, debug triggers, trace styles and much more.

• WPF Performance Suite
  

  The WPF Performance Suite enables you to analyze the run-time behavior of your WPF applications and determine performance optimizations that you can apply. The WPF Performance Suite includes performance profiling tools called Perforator and Visual Profiler.

Paid Tools:

• Mole 2010
  

  Mole is a debugging tool for .NET developers.  It can be opened in Visual Studio 2010 while you are stepping through your source code after hitting a breakpoint.

  Mole was implemented as a custom debugger visualizer so that you can easily use it just like any other visualizer available in Visual Studio.

  With it you can navigate object graphs, view collection data, inspect visual elements, drill into data bindings, sort and filter object properties, compare object snapshots, and more.