The best man is a great job to have because that means you are close to the groom and you support him in everyway.
WELL, many moons ago this job was taken very seriously. The job of the best man was to protect the groom and the bride from the brides family. If a groom could not find a bride that was in his community, he would capture a girl to be his bride. This of course is not a one man job, so he would bring along his companion, later to be known as the best man. The kidnapping of the bride would anger the family which would usually lead to a fight to capture the girl back. Therefore, the best man had to be prepared for any revenge doing by the brides family and be the one to stand guard and protect the bride and groom. During the ceremony the bride would stand on the left side of the groom so that his right arm was prepared for any fighting he had to do, while is left arm was to protect his bride. The best man would be by the grooms left side armed and ready to fight. The best man was a job taken extremely serious and a job needed to be done right.
So, men get your weapons and be prepared because you never know which crazy uncle disapproves of their niece getting married to your best friend.