There's nothing like a toy gun to make a boy's evening.
Here's one my little man loved -- the Rapid Fire Power Popper, which retails for $16.99 from Amazon, Learning Express and Vat19.com.
With the press of a trigger and by sliding a handle to and fro, the gun fires lightweight foam balls out of a see-through chamber. There are 12 balls, which can be shot in a quick, almost machine-gun-like succession by sliding the handle fast.
My son, Harrison, who is 8, said it was better than the Nerf guns he has owned because of the automatic action. But beware: The balls can be easily lost in corners or under couches, so be prepared for some frustration.