One of the most invaluable accessories you can keep in your camera bag is a small step ladder. Ok, technically not in your bag, but you get the idea.
It comes in particularly handy when you are taking someone’s headshot and you want to maximize their positive features while minimizing the not so positive ones. Depending on your subject mileage will vary but it is safe to say that everybody looks better from a slightly downward angle vs straight on. (This is generally a pleasant euphemism for “double chin de-emphasization”)
As an example I shot a quick series of 3 headshots of Meike. Now, as it turns out Meike has very strong, photogenic features (just the one chin) so the differences are very subtle but they are noticeable. The first shot is straight on, second shot is from one step up and the last shot is from the second step.
Even though the difference is subtle in this case I always make sure I have the step ladder on hand for this kind of shot. (Shot with Canon 5d MKII and 70-200mm f4L).