How much of a charge can a human body build up from static electricity?
This question is a bit like "How long is a piece of string?" The answer depends on various factors and circumstances. We tend to think in terms of voltage rather than charge, because as the saying goes, "It's volts that jolts" - in other words voltage, rather than charge, causes us to feel a shock. About 3000-4000 Volts on the body will cause us to feel a shock when we touch some object. A shock felt when getting out of the car may be caused by a body voltage of about 10000 V. Body voltages up to 35000 V have been reported, but I see no reason that higher voltages might not be possible in exceptional circumstances. Body voltages up to 10 kV (10000 V) are commonly responsible for the shocks we feel in daily life, and are largely caused by insulating flooring, footwear and furnishings. For more information on this see my article on Static shocks and how to avoid them.