The brief history of manned space flight has been largely a pacific one, with such combat-oriented aspects of it as there have been being limited mostly to missiles or orbital lasers--and mostly only in theory, at that.
Have two space-farers ever had cause to fight one another while on a mission, though? I don't mean two from competing countries during the Cold War, or anything like that, as I'm sure that would be an event I couldn't help but have heard of; instead, I'm wondering if tensions have ever boiled over on Mir or Skylab, or on a shuttle mission. I won't ask about the ISS due to the 20-year rule.
This is a pretty trivial question, all-told, but it occurred to me that a brawl in zero-gravity would be pretty interesting.
This isn't two astronauts fighting in outer space (though it's entirely plausible that the crew did), but you might be interested in the Apollo 7 mission.
Apollo 7 was the first manned Apollo flight, and it lasted 11 days...long story short, space sickness became an issue, the commander Wally Schirra came down with a nasty cold which the others soon caught, and they spent the rest of the mission arguing and fighting with ground control.
Schirra had already announced he was going to retire, but the other two never flew again due to their conduct on that mission