In my opinion the best photography "Effect" is the one that is never used.
Perhaps I'm more of purist than most but I dislike most of the "Effects" people add to photographs to "Improve" them. Personally I'd rather see this group of photographs as they came out of the camera rather than with these effects applied to them. To be clear, I don't object to editing photographs to improve the natural appearance of them, I simply dislike effects that distort the appearance of an image. In my personal opinion adding grain, adding colorization, adding vignettes, adding posterization, and a host of other effects, does nothing to enhance anything.