Mine would be Mr. Doob's Hi-ReS-Stats:https://github.com/mrdoob/Hi-ReS-Stats
Good answers so far.
@Philippe, I've had that ColorMatrix class on my HD for awhile; I'll have to play with it.
@jpauclair, There is an artist at Firaxis who *LOVES* your profiler; it's like he's playing the "eliminate draw calls" game with his creations.
@elyon, good stuff... is there a single class though you cannot live without?
All, would love to hear others, who have yet to respond, to chime in... (with links)