[Supraball] is first person multiplayer sportsball.

AkimboEG

Supraball is football (soccer for you 'muricans) played in first person with other people.
It's currently in development by some Europeans with funny names.
As the developers put it,

Supraball is the official successor of the infamous "Deathball", a Mod for Unreal Tournament 2003/4 that first came out in 2002 and won plenty of awards.

Trailer
https://www.youtube.com/watch?v=9FyW5m5XGZU

Gameplay
https://www.youtube.com/watch?v=r5KCFRlwd_8

It's quite a bit of fun when you've got two roughly equal teams.
Even if you don't know anything about football, you'll learn everything you need to know within a few minutes.

Some things not immediately obvious:

• When you have the ball: LMB to charge and shoot. RMB to pass.
• When you don't have the ball: Thumb button / Ctrl to catch the ball, left click to volley (shoot without catching), right click to shield (repel ball).
• Holding Q or E when shooting / volleying will curve the shot sideways.
• Holding Thumb button / Ctrl + RMB lets you dribble.
• Passing is predictive - the ball will go where the receiving player will be if he keeps moving in the same direction. So when receiving - either stand still or keep moving in the same direction.
• You can push opponents with LMB. Doing this on the player with the ball will hurt him, potentially making him drop the ball. You can (and should) boost your teammates the same way.
• Goalkeepers can dash with Shift or double-tapping. Double-tap dash can be disabled. GKs are invincible to enemy attacks.

Go kick some balls. And say hi if you see me ingame.

Gaslight

OK this looks fun and unique. I can't think of any other first-person sports game besides... what was that (American) football game? Backbreaker? But I guess even that wasn't really first-person.

TychoCelchuuu

If you buy Probably Archery it comes with Zombie Soccer. That's a first person sports game.