j00sux

noun/verb thing
It's 1337 for 'you suck'
"You Suck" -> "ju Suck" -> "J00 Suck" -> "J00 sucks" -> "J00 Sux" -> "j00sux"

often used by n00bs, but also used by geeks to get a reason to mock an non-geek

(N00B_00 was killed)
N00B_00: OMG!!!1!!!!J00sux!1!1!!!!