It has become a favourite activity at stag parties and for those who enjoy rough-and-tumble sports.
Now doctors have warned about the dangers of paintballing - after a teenager's liver was damaged during a game.
In the first recorded injury of its kind, the 18-year-old needed treatment to stop extensive bleeding from the organ.
The case has reignited concerns that the game's paint-filled capsules - which travel up to 300ft per second - can cause potentially major injuries.
Writing in the online journal BMJ Case Reports, doctors described the unnamed teenager arriving at hospital with symptoms similar to appendicitis.
But when surgeons at North Middlesex University Hospital, north London, looked into his abdomen with a camera, they found extensive bleeding from the liver.
They then had to open up his stomach so they could stop any further bleeding. After the operation, it emerged that the young man had been paintballing a couple of days earlier.
He described being hit twice on his right side - though no bruising or marks had appeared on his skin. Doctors Joshua Luck, Daniel Bell, and Gareth Bashir wrote: "This represents the first report of paintball-related traumatic liver injury."
They added that organ injuries "of this nature" had only been reported three times before - to the kidney, penis and scrotum. An operation was needed to correct the damage to both injuries in the groin. The doctors added: "Participants and physicians must both be aware of the possible dangers associated with this sport."
Paintball rounds are already a recognised cause of eye, face and scalp injuries.
But the report shows that internal organs are also at risk, the doctors conclude. Physical contact - apart from shooting with pellets - is forbidden during paintball, and participants wear masks to protect their face.
A study in 2002 found that an estimated 923 patients attended A&E in the UK after an accident while paintballing.
Almost half of the injuries were to the leg, ankle or foot, accounting for around 431 of those admitted, according to the Royal Society for the Prevention of Accidents.
Strains and fractures were the reason 42 per cent of the victims went to hospital, with a national estimate of 390 for that year. A significant, though not so high, number of injuries also occur to the hand and arms.
The first paintball guns were developed in 1970 so farmers could mark cattle from a distance. The first organised paintball game took place in 1981 and since then its popularity has soared.
Men account for just over 80 per cent of those hurt in the game. American research showed that the body part most commonly injured is the eye - however it also found that the vast majority of these victims were not wearing their face mask or goggles.