Those weapons carried by the soldiers at the Battle of Gettysburg were in no way different from the ones used at other points of the war. Just as war has always been practiced, weapons influence tactics and this article lists a variety of Civil War rifles and artillery pieces that were put to use during that three day battle. The author also goes to some length describing the manner in which Civil War regiments and brigades marched into battle and the deployment of their supporting artillery batteries.
It was on the first day at Gettysburg that the Confederates made a terrible mistake. Read about it here.