I could see Football (Soccer to the yanks) being quite a popular sport in the wasteland: Its requires only a big field of dirt or grass, a ball (which can be easily made from brahmin leather or something like that), something to be the two goals and a few people, with 22 people or more if you really want to go at it.
Also, unlike American Football, Rugby or Baseball, the equipment required is quite few and easy to obtain, and football isn't as violent so there's a lot less risk for contusions, broken limbs and bones, etc.
Football could be a good way to entertain people, and keep in shape and encourage teamwork.
I can see the Legion doing a american football-like sport, through, violent, brutal, requires strength and endurance, they even got the gear for that. Imagine a bunch of pre-teen legion kid soldiers playing american football during their off-hours. Hey, Legionnaries have to do some R&R too!
I'm surprised archery ins't helluva popular in the wasteland; Hell I find it ludicrous that tribals don't use bows or crossbows. A bow or a crossbow beats some nailboard anyday of the week, and they're a easily-made weapon that could be easily produced for bands with scarce firearms, and for ammo all you need is some wood and perhaps a metal tip.