Airsoft guns are replicas of real firearms designed to shoot plastic pellets instead of live bullets. They are used in many situations from historical re-enactments to military training. Making targets for an airsoft rifle is not difficult. The weapon still has power to penetrate a paper target or knock over tin cans, so there are a wide range of targets that can be used for practice.
Print a circular target on standard printer paper. At relatively close range, depending on the gun's power, the pellet should go straight through the paper -- but not far enough to cause any safety problems. There are numerous websites where both standard and novelty targets are available for download, or you can create your own target with a marker pen.
Set up tins cans like at a fairground. Empty cans make great targets. You need to hit them accurately to get them to fall, and they make a satisfying noise. As airsoft pellets will not go through metal, these also have the advantage of not requiring a pellet trap to stop the rounds.
Purchase a metal-outline air rifle target set. These are spring-loaded metal outlines of animals, objects and people. The targets are made out of metal so the pellets will not pass through them. The target sets usually come with a pellet trap built in to collect the airsoft rounds.
Assemble a sticky target in your room or back garden. Sticky targets, which can be purchased from many airsoft retailers, are covered in a gel which holds the pellet to the target for a few seconds so you can see where it hit the target. The pellet then drops into a tray so it can be used again.
Airsoft rifles do not require the same level of safety as real weapons, but eye protection must be worn at all times.