Airsoft is a fun and active military simulation sport in which many participate. It is much like paintball, except small plastic pellets are used as projectiles.
Some manufacturers now offer intelligent targets for train or just fun shooting at it.
I was going to build something similar using an arduino. I still have not decided what type of sensor. After seeing some of the alternatives on the market it looks like it could be a piezo or if the target is enclosed rubber a barometric sensor. I would also like that could determine the impact score (position) so I'm looking for guidance.