Where can I buy Nerf Guns? Find Answers in Comments

Walmart and Toys R us

Most department stores and toy stores will carry the normal Nerf guns.

If you want your guns to shoot further, consider buying a modded one or mod one yourself if you are good with “do it yourself” projects. Hasbro (Nerf company) adds air restrictors in the guns. They make the guns quieter and safer, but they reduce the range of the gun significantly. People will remove these to give many guns almost 2 times the range. Other mods that people will do to the guns include adding a stronger spring (again, longer range) and painting the gun to look better. These guns will cost more money, but they are usually worth it for the extra range.

Check the sources for links to popular guns.

You can get Nerf Guns and Darts and all the accessories you need at Target. Many Nerf Guns are Target Exclusive, so you are better off going there; they often offer a whole isle just for Nerf Guns. Also, for a smaller selection, go to Toys R US.
Hope this helps