Nerf came out with a series of guns and they've been pretty aggressive with the lineup, frequently changing it around and introducing new models. OK, so I haven't tested all models, like the impressive N-Strike Vulcan. But I am seeing a lot of lazy design in the guns I have checked out thus far, including the N-Strike series guns Nite Finder Blaster and the truly horrible Recon CS-6. We tried to give my son the Rapid Fire 20 and it was a complete disaster -- you have to pump it up over 30 times and it gets *really* hard to pump after about 25 or so.
The only gun that seems to work reliably and not require a lot of fuss is, no surprise to real gun aficionados, a revolver. It's the N-Strike Maverick. Aside from looking really cool, the gun is easy to load, can be cocked by a kid, and reliably shoots whatever you put in it. Unlike some of the guns Nerf has made, each with a variety of design flaws, the Maverick handles ammo well. Some guns will only accept certain ammo, but the Maverick work with snub nosed ammo, suction cups and whistlers.
For the money it's hard to beat the Maverick in style and quality. There are even mods out there that make it cool for older kids!