In my opinion the least violent sport in the world is chess. Other sports that are not aggressive include: rope jumping, snooker, falconry, volleyball, badminton, athletics, bowling, darts, handball, net ball, table tennis and tennis.
I don't consider poker a sport but apparently some people do because poker playing is shown on some sports television channels. From my point of view it's a tremendous waste of air time for a traditional sports fan such as myself. But - if it's to be considered a sport I'd consider it the least dangerous unless the participants are armed and have the old west mentality