The deadliest weapon in space

That comic is so wrong it hurts. 1) Troll physics at its best. To make it simple: A nerf gun transmits kinetic energy via the bolt it shoots and by that you have an action and an equal reaction. Therefore, the force is applied equally to both astronauts. 2) A normal gun would work perfectly well in space up to the time it becomes to cold to operate. Oxygen from the environment is not required as the gun uses the oxygen stored in the ammunition. That is the reason why modern firearms can be fired under water.