What is the maximum weight for a pilot to use the ejection seat in an F-100 fighter?
Firstly, welcome to Aviation Stack Exchange! As for your question, I actually could not find the exact model used for the F-100 series (sorry), but as far as I can tell most American first and second generation jet fighters were installed with Martin-Baker Mk.1-3 ejection seats. These were some of the first examples of explosive charges being used as the main propellant, and for the sake of a shorter answer I will assume you understand their basic operation. The Martin-Baker website states that the for the given size range of crew (between the 5th and 95th percentile), the seat could manage to lift a 224lb pilot/aircrew at a maximum of over 400 knots indicated airspeed.
[Edit] I want to address @GypsyRanger's answer: I think we can all assume that the pilot being ejected from the fighter has undergone and passed Air Force criteria for qualification to be a fighter pilot. I personally think his question is simple but a good one because he is just asking the weight limit, and in terms of mass this shouldn't be too hard to answer. I myself couldn't find the exact model, but all main-stream American jet fighters of the F-100's era were fitted with Martin-Baker seats ranging from the Mk.1 to the Mk.3. If you take the time to look at the specifications for each and compare, or knew beforehand you'd know that the improvements between each model were mostly pertaining to reliability and safety for crew, something that they were lacking in at the time (the firing mechanism was practically the only thing changed throughout). Really though, don't be too quick to criticize if you won't put in the time to read it or because it's a short question.
Depends on a few variables, including the amount of separating power the ejection seat has, and most of all how tall the pilot is. The current weight limit pertains to and is based on height. Pilots have to meet the Air Force's height, weight and physical conditioning requirements. They must be 64 to 77 inches tall when standing, and 34 to 40 inches tall when sitting. They must weigh 160 to 231 pounds, depending on height. But, the question is a bit too broad because you do not list the variant of the fighter and what type of ejection seat and launching system is used.