Building LEGO replicas is one thing, but building working replicas of guns in LEGO is something entirely different. Check out this reproduction of the NERF Maverick REV-6 blaster by AstonishingStudios. This is some awesome LEGO engineering.
This fully-functional blaster uses only plastic bricks and a metal spring for power. It fires standard NERF suction cup-tipped darts, but each had to be shaved down just a bit to fit into the gun’s rotating cylinder. It is a faithful recreation of the original NERF toy that you terrorized your parents with back in the day.
It’s probably more expensive to build this out of individual LEGO pieces than to buy the actual NERF gun, but it is nice knowing that it can be built if one has the skill.