Originated on LS1.com, now on LS2.com, a member named MJSBossman punched a 12 year old boy at the movie theaters because he was being an annoying little prick, the term was coined by Bravo on LS1.com. Variations included PYITS, PMITS, PTITS etc
That guy was pissing me off, so I PHITS.
MJSBaldman punched a kid in the stomach at the movie theater, so Punch Him In Teh Stomach=PHITS, another variation is PYITS
If he doesn't shut his mouth, I'm gonna PHITS.