Nerf guns can be fun if you're a grown-up -- just ask the legions of people who modded the Maverick revolver. They're not really intended for an older audience, however, which is why Hasbro just unveiled a range of Nerf blasters meant for high schoolers (and adults) who take their plastic weapons seriously. The highlight is the Rival line you see above, which shoots foam balls at nearly 70MPH -- they won't sting like paintball rounds, but you're definitely going to feel the blow. You can get the $50 Zeus MXV-1200 if you insist on fast motorized reloads, or the $25 Apollo XV-700 if you're content with lever action.
Hasbro hasn't forgotten the customization crowd. Its $50 Nerf N-Strike Modulus (below) is designed to use $15 upgrade kits that change the dart gun's role; you can turn it into a close-quarters shooter or a long-range rifle, and there's even a stock that doubles as a backup gun. You'll have to be patient if you're eager to upgrade your arsenal, though. Neither the Modulus nor the Rival line are shipping until the fall, so you'll have to make do with the existing range during summer vacation.