Growing up as a teenager in the late-90's and early 00's, I went deep into paintball.
A lot of friends of mine today kind of chuckle when I tell them I used to travel and play in a national tournament series, but what a blast it was!
There's great history here. The big American league at the time I got involved was called the National Professional Paintball League (NPPL). The flagship competitions were 10v10 capture the flag, and they also had 5v5.
The NPPL at the time was broken down into Pro, Amateur A, Amateur B, and Novice, with 8 or so tournaments per year culminating in the World Cup in Florida.
There was a pretty exciting ecosystem at the time, with tons of exciting paintball marker innovation happening as markers were making the switch to electronics for the first time with the WDP Angel (a European company), the Smart Parts Shocker, and others to follow.
Not to mention the mechanics of the old non-electronic markers like the WGP Autococker and the Automag. The geeky bits of which would absolutely fascinate all the technical minds of Hacker News.
(for example, check out some of the cut-out animations of the mechanics of some of these old paintball markers. Customizing and tuning and adjusting were a total blast back in the day. Way cooler than pogs! http://www.deadlywind.com/paintball-animation)