Which one do you use, for what kind of job and why?
When I have complete control of the lighting, like on a set, I usually try to get an in-camera look as near as possible to the final look I want to get, so I usually create a specific style for each film, modifing an existing style or creating a new one with that infernal tool that is Canon's Picture Style Editor. Unfortunately I don't know about any other software that can do the work...
When I don't have control over the lighting and I know I won't have much time for the color grading, like when I'm shooting events or corporate videos, I usually choose the "Neutral" style, setting sharpness to "0" and sometimes lowering the contrast as much as possible.
When I don't have control over the lighting but I know I'll have time for a proper color grading, I often use the Technicolor CineStyle v1.0, which is the only "flat" style I really like. And the only one I know that is able to increase so much the DR, without showing too much noise.
These are the picture styles I tried so far:
Technicolor CineStyle, Marvels Cine, cineplus Picture Styles, Canon Video Camera X-Series Look, Flaat picture styles, ExtraFlat Picture Style, Superflat Picture Style
What about you?