My fault for stating it as a bright line rule. As I've been reminded frequently, "Bright line rules are for idiots".
"Consent" is a valid defense, but has its limits. You can't give someone else permission to break the law. Boxing and MMA are regulated sports with licensing commissions and rules. When the fighters abide by the rules, it's not assault. If the meth were particularly strong that day, and one fighter pulled brass knuckles out of his bike shorts, it could be criminal. Hockey players have been charged for using their sticks to bludgeon an opponent.
Sadomasochistic play is likewise tricky. Usually, there's a consent defense. When body parts start being removed, consent won't be a valid defense.
I feel pretty confident in saying that no judge is going to recognize consent as a defense to shooting each other with handguns. Now, no one was hurt, and the crime against society was pretty minimal (they're not likely to shoot at strangers who AREN'T wearing body armor). No one really needs to go to jail for 5 years.
Texas would allow something like a 5 year sentence suspended (you wouldn't go to jail at all), with a period of probation (2-10 years or something) where you'd have to surrender your weapons, meet with probation officers, and obviously not get in trouble for that period. Once complete, the crime would basically go away.