There are no real life bullets no projectiles to fire. Then, make up a video game where you can go around with these guns and shoot at real-life people.

Then make 'real life' versions of all the guns in Doom, like the Super Shotgun, etc. Put a chip in each person's body that is used to regulate their critical functions (heart, lungs, brain, etc.) through the Internet. Or here is one of the best airsoft stores in the world (with it's main store located in Japan) Besides, I don't think their's a gamer I know who never heard of paintball And 90% of the people who play games like CS love airsoft (after they find out it exists.) You can check out some of the guns and info here I've even seen a few anime's where some of the main characters would play airsoft (like all the time and they'd always talk about it in all the episodes, not like one time and forget about it.) I don't think their's a show in america where any of the characters play paintball. The guns fire small plastic BBs that hurt less than paintballs (but fly farther and are way more accurate.) I know a bunch of people who play it in the states (like half the number of people that play paintball play airsoft) but in Japan it is much more popular. It has replica's of pretty much any gun available in the world (and if it's not available, build it yourself) this game is VERY popular in Japan. Or, gamers could just discover paintball.

Doom real guns advanced