tug of war!
Depends on what the question refers to: The longest "running" event is the Marathon, but the longest event in terms of distance in the athletics is the Mens 50 kilometre walk (but you certainly aren't allowed to run in that). Alternatively there are a whole series of events that have been included in every Olympics, therefore there is no single longest running event in terms of being at every Olympics.
Women's Boxing
Archery was a sport at the 2016 summer Olympics. Artistic gymnastics has been a Summer Olympic event since the 1928 Olympics. Alpine skiing is a Winter Olympics sport.
Yes, ice hockey debuted at the 1920 Summer Olympics in Antwerp because, at the time, there were no Winter Olympics. Ice hockey has been a Winter Olympic event since the first Winter Olympics in 1924.
There are many, many sports that have not been events in the Olympics
Figure skating was an event in the first Winter Olympics in 1924. (Prior to that, it was actually part of the Summer Olympics in 1908 and 1912.)
Summer Olympics: 1976Winter Olympics: 1988Winter Olympics: 2010
In modern times, the first Summer Olympics was in 1896.
Ethiopia first participated in the Summer Olympics in 1956 and has been to every Summer Olympics, except the 1976 Summer Olympics, since then.
USA has been in every Summer Olympics, except the 1980 Games, and every Winter Olympics. That makes USA competing in 25 Summer Olympics and 20 Winter Olympics
No, it's still in the summer Olympics.