Normal rules are that your IFAK is only for use on you, but that assumes a) active combat, and b) everyone carrying one in the same place so others can kind it and c) everyone being trained to use it; do what makes sense in context.
Folks who have advanced training might want to add more stuff, but at that point you know what you like. Specifically, I do not recommend carrying decompression needles or nasal-pharyngial airways unless you've been trained on them — they're unlikely to do much good without training, and the needles especially can cause real harm if used incorrectly. Note: I am trained in first aid, but I'm not an EMT, etc. I have, however, spent a good chunk of time digging into stuff here and talked with friends with more training about it extensively. Happy to hear opinions from other folks with more training here too.