The three football tragedies Bradford, Heysel and Hillsborough along with the Iranian Embassy, first Space Shuttle disaster, Chernobyl, Reagan & Pope assassination attempts and finally the first Gulf War and 9/11 are the events that have the strongest memories for me. Definitely a bias towards eighties events and when the realisation hit that the world is dreadful at times and will always throw up new tragedies.
Cambodia, Ethiopia, Waco, Oklahoma City bombing, Tiananmen Square, Manchester Arena, Airey Neave, Mountbatten, Ross McWhirter - loads of things that stick in the mind.