Making decisions based on very little information, using a combination of experience, clinical skills and gut instinct. You have to know sick vs not sick, everything else is just details.
You should be able to see patient rolling in on a stretcher, and with their vitals, CC and PMHx and a spot physical exam tell whether they will be discharged, admitted to floor, ICU or morgue. You should also be writing orders now. Door to dispo in <2 minutes. Of course, you will have a few complex patients where you don't know that answer immediately, but I'd say 80% of my patients fall in this category.
This skill, when used correctly, gives you sufficient time to think about your 10-20% of patients who are either complex or sick.
Quick decisions take courage and confidence, and is why EM docs are often referred to as cowboys. Many times we are WRONG, but that doesn't mean we can afford to slow down. Other services love to laugh at how stupid we are because our initial diagnoses are often wrong. Making diagnoses is not my job.
If you are someone who needs more time to decide what you want at the restaurant, you probably shouldn't be an ER doc.
All of the other things: multitasking, thick skin, sense of humor, physical fitness and endurance, are also very true.
Also a great love of free time...