hmm....
"mouth-breather" to describe some form of cretinous stupid-face (after the manner in which they wander around with mouths agape when not spitting in the street)
"oaves" to describe a group of the above. Not so much slang as the rarely-used correct plural form of "oaf"
"crikey fuckballs" and "fuck my best badger" were handy exclamations at school though I use them rarely now...
"spunnet" to describe someone of the nature or manner of a spong™...
"numpticulate" to describe someone with the characteristics of a numpty...
Current workplace wank-speak includes such things as "dirty" for processes with too many "waste" steps in which don't "give value" (sic) to the customer (which are discovered through "check" { the process of studying a department and their entire range of tasks in order to build up a picture of the customer demand for the area}).

There's also the classic "have you tried logging out then back in again" or "switch it off and leave it for ten seconds then try again" which translate roughly as "I'm an incompetent fuckwit who can't be arsed to try and find decent solutions to problems"
( wingpig wish I'd known about liquify eighteen years ago, Wed 4 Feb 2004, 6:56, Reply)