N.F.U. No F**king Use (applies to kit and individuals)
N.F.I. Not F**king Interested (as per Woopert, but slightly more motivated :-/.)
W.A.F.U. Wet And F**king Useless (Normally a term of endearment for the Fleet Air Arm).
JAFFA - Just Another Fat Farking Administrator
PONTI - Person Of No Tactical Importance
FUBAR - Farked Up Beyond All Recognition
SNAFU - Situation Normal, All Farked Up
PSG - Potential Security Guard - Reg NCO nearing end of engagement
FIS - Future Insurance Salesman - Officer in same state
APFSDS(T) - Armour Piercing Fin Stabilised Discarding Sabot Tracer - I know this is true, not funny but I like it anyway
FNU SNU (First Name Unknown Second Name Unknown).
Not in itself funny, but hilarious when a Rupert who shall remain nameless becomes convinced it's a real Bosnian chappy who keeps popping up all over the place...
Attending one of my various service schools, the instructors were usually ensigns directly out of college. It was a deal that the US Navy would pick up their college loans if they serve a certain amount of time as instructors. Most of em were woman.