How would anyone feel if Batman took out a katana and did something like slice a criminal's gun in half? He does know how to use one, and it would be different. The blade could extend from and retract back into the handle when not in use,being able to fit on his utility belt.
Justice League?, The Avengers 2, Star Wars Episode 7, Fantastic Four, Warcraft and Ant-Man... The world isn't prepared for 2015.