Various job postings for Tools Developer require different skills. Some require C#/NET and WPF while other have as nice to have Max, Maya dev skills. I would like to ask based on your experience, what are the most really needed skills that in the end any gaming studio will require when hiring.

That very much depends on the company. 'Tools' is a pretty broad description. Sometimes it means writing custom Maya/Max plug-ins to set up custom shaders, level editing, data export/import etc. Other times it involves writing custom MySQL asset servers with some form of C#/HTML5 front end. It can also mean writing large scale stand alone level/character authoring tools.

Generally (imho as a former tools team lead) the best people know about Maya and/or Max, both in terms of their API's, and as a user (because understanding how the artists work helps you write better tools). They are also very good at writing solid, stable, well tested C++/C#/Python code. Extremely good knowledge of Matrices/Quats/Vectors is an absolute must (because attempting to flip coordinate systems, whilst baking out scale & pivots, is one of those annoying and common tasks). Experience packaging assets for use in runtime is really useful (fix/unfix pointers, 16byte aligned data structures, data compression, etc). Knowing how to use VTune always comes in handy (because everyone hates long asset processing times).

Thank you for the reply. I have Winforms and C# experience and been using WPF for the last 2 years. I am more of a developer but have used Max and Maya not as an artist but general user. Thank you for giving me the inside information since it is always the best :-)