I have my standard headphone testing tracks:

Generally: Aether - Illusion: Perfect for testing bass and dynamics.

Basically everything that Qumu makes, he/she produces very high quality gaming remixes, if you like that stuff.

Also "Theophany", same category, same incredible quality, different style.

Surprisingly also the soundtracks of a lot of Korean MMOs, incredible production quality: Blade&Soul(<-) ; LineAge / 2; Aion...