InFAMOUS: Second Son has no shortage of Easter eggs, including nods to fellow first party PlayStation series, Sly Cooper. Perhaps the most interesting, though, is the appearance of the Master Sword from Nintendo's The Legend of Zelda franchise. Granted, it's not an exact replica, but pretty close.
To find the Master Sword, simply walk into Eugene's house and look for it near the laptop. That's it! You cannot interact with the weapon in any way, but it's still fun to discover.