What sport needs the quickest decision?

[AK ref SE]

I had a conversation with a player of many different sports in my office this AM. He was frustrated at this one particular softball umpire for making quick calls on whether a player was out or safe on a close call. I gave him my reasoning why this umpire may have been doing this. we brought up several sports and reaction time to make the call. I gave him my answer on what sport I felt that you need to make quick decisions on.
So my question to the forum, since I do not do all sports,
What sport do you feel needs the quickest decision to make a call? And Why?

AK ref SE