I'm a biker
and that means I get cut up in traffic fairly often, by people who just aren't paying enough attention. When I get chance, I like to pull up alongside them at the next lights or junction, and point out to them, calmly but firmly, the error of their ways.

"Oi, Erma, did you not see me back there or what?"

As this is delivered quite calmly, they'll often pick up on the odd name and tell me their name isn't Erma. At this point I can crank the volume and point out that:

"It's an acronym - means Excuse for a Retarded Monkey's Abortion!"
(Leo Sasquatch hates being the grown-up, Tue 9 Oct 2007, 22:46, Reply)

5 yr old insults
the worst thing that me and my 5 yr old can call each other is "monkey bum baby bottom biter bum baby bottom bum baby burp".

don't ask, i don't know........
(brocky, Tue 9 Oct 2007, 22:38, Reply)

another one
Nobby nobby nob nob

No idea where it came from, but has more impact the higher you can say it
(brocky, Tue 9 Oct 2007, 22:37, Reply)

see you....
"see you, if you was on fire, I would watch and warm my hands on it. Then I would wait and wait until the last dying ember. THEN, and only then, would I piss on you."

(first post, long lurk, be nice)
(johnnyevil, Tue 9 Oct 2007, 22:24, Reply)

In Brooklyn
A few weeks ago, I heard a kid shout at a pack of frat boys:

"Oh yeah? Well, that's why your ma went to Clown College!"
(Spiderbaby O_o, Tue 9 Oct 2007, 22:10, Reply)

A couple
I called someone a cockpit once, the twat went "oh so im a cockpit am i, well whats that then?" trying to be smart but obviously missing the reference. "its where you take it up the arse you dozy cunt!" he went a little red.
-
After a heated childhood slanging match andrew was all out of good insults, i called him a cocksucking horsebanging shitbag. he replied with this absolute gem "well youre a.............. a.... BLOODY GIT!" ive never laughed so much in my childhood.
(cantbearsed I cant be bothered to write a sig... wait, Tue 9 Oct 2007, 22:06, Reply)

Ziderman2001
you reminded me of Johnny Dangerously with his Ice hole, and Fargin Bastages. You cork sucker and

You fargin sneaky bastage. I'm gonna take your dwork. I'm gonna nail it to the wall. I'm gonna crush your boils in a meat grinder. I'm gonna cut off your arms. I'm gonna shove 'em up your icehole. Dirty son-a-ma-batches
(lordy lordy, Tue 9 Oct 2007, 22:05, Reply)

PISH
From Scottish TV series "Rab C. Nesbitt"-

"Away an' lie in your ain pish!"

or a local favourite here -

"Away an' throw shite at yoursel'!"
(powersquirrel, Tue 9 Oct 2007, 22:01, Reply)

Blunt
I used this today:

"You ugly, pointless sack of of shit"

Was that harsh?
(james_tiger_woods is going to start his killing spree on the, Tue 9 Oct 2007, 21:54, Reply)

After being out and getting far too drunk
in front of stuffy work colleagues...me and my mates always called ourselves pigdogs...(sobbing quietly into coffee wondering if we were going to get the sack on monday) LOL!
( curvylittlegoth heard the voices in your head on, Tue 9 Oct 2007, 21:49, Reply)

A tenant of a flat near ours ...
... used to wander the estate shouting "grrrrrr .... WANKDOG!!!"

Later we worked for the same council housing office and found that the tenant used to write long letters making free use of this lovely word. It's now our favourite swear.
(boredcouncilofficer, Tue 9 Oct 2007, 21:30, Reply)

probly bindun

(ManToe all he learnt in sex class was 2 clean his armpits, Tue 9 Oct 2007, 21:29, Reply)

I heard some eleven...
...year old kid call his friend a stupid monkey jew baby.

That is kinda the most pathetic insult I have ever heard.
(chessboardhearts "I don't touch the bodies.", Tue 9 Oct 2007, 21:25, Reply)

/Unlurk
Horse's minge

/Lurks
(powersquirrel, Tue 9 Oct 2007, 21:20, Reply)

ziderman2001
Has reminded me of my all time favorite rudeboy.

Mother-What do you want for your birthday dear?

Rudeboy-Twat on a brick, now fuck off.
( The Awful Puppy Bakery is still bored, Tue 9 Oct 2007, 21:00, Reply)

joan.
youre a bigger cunt than joan collins.
(shes probably very nice?)
(brussellsprout Im a fucking genius. official., Tue 9 Oct 2007, 21:00, Reply)

i coined a pretty special one today...
wank captain. i said that my flat mate emily had used it on me, to general laughter and consternation, and then admitted i'd just made it up to make her look bad.

then we nicked her keys and changed one of her keyrings so it said "wank captain" on one side, and "jizz head" on the converse. good times.
(notjustahatrack peeling a sausage..., Tue 9 Oct 2007, 20:58, Reply)

When I'm in my little car, I generally swear like a navvy
Though having said that, I do get a lot of "tosspot"s to the gallon...

Some of my favourites are:

arse-nadger
twatbasket (or twatbarrel)
fuckwit
arsewanker

and, inexplicably, 'monk-fish'. I really couldn't say why.

When my brother was a cub, his troop (pack?) scarf was West Ham colours. Just calling him an HP Sauce bottle could practically reduce him to tears.

And we once heard our neighbours' grown up son shouting very loudly that his father was a whore-monger and his mother was a whore. I don't believe either epithet was accurate.

Length, relevance, yada yada yada....

EDIT: and at the moment, I'm enjoying using 'Ya hure' (3 syllables) at every opportunity.

EDIT EDIT: And 'wankstain'
( b3th Not shit. Not mod., Tue 9 Oct 2007, 20:47, Reply)

Might be on here already but I ain't seen it:
At Reading festival back in 2001/2/3 whichever... I frequented the comedy tent lots.

Comedian was telling a story about some kids at the back of the bus trying to put eachother down:

"Yeah? Well your mum still owes my dog fuck money!"

Probs untrue, but the sound from the main stage was so loud (probably from Iggy Pop) that he got about 300 of us to shout it at them in a quiet bit.

True.
(tweebianmonkey Should be known as Widget, Tue 9 Oct 2007, 20:26, Reply)

When I was about four
I called my mum a catalogue.

You... you... CATALOGUE!

That's quite cutting for a four year old.
(woohoo, Tue 9 Oct 2007, 20:24, Reply)

I'm on a roll!
ALways liked "I've a soft spot for you... the peat bog at the bottom of my garden"
(ziderman2001, Tue 9 Oct 2007, 20:16, Reply)

qotw
I just called my g/f a big bag of whore.
She was not suitably impressed.
( Maffers I flow kinda strange like Spina Bifida footprints, Tue 9 Oct 2007, 20:14, Reply)

you
self indulgent, self centred, adolescent, touchy fucking brainless cocking twat who needs to get OVER HERSELF YOU SILLY COW

GROW THE FUCK UUUUUUUUUUUUUUUUUUUP
( writerblock ... embedding disabled by request on, Tue 9 Oct 2007, 20:14, Reply)

insult
fucking slore...my friends 19 year old son explained its a cross between whore and slut. just doesn't get any better then that
(deja, Tue 9 Oct 2007, 20:13, Reply)

Spazzhat

(moomin-papa ; folkin class., Tue 9 Oct 2007, 20:12, Reply)

My missus
Lovely girl, amazon woman!
Takes great delight in belittling the vertically challanged with the apparently well known phrase....PORG

Person Of Restricted Growth

Certainly sorts out the men from the boys!
(ziderman2001, Tue 9 Oct 2007, 20:09, Reply)

badboys piss take
I think it was the fast show where they were doind a sketch and replaced true swears with other words.

Fun you, you funnin funner, I never ducked your wife.

or

Arnie pisstake (I still use this, not sure where it came from)
Fun you airhole!
(ziderman2001, Tue 9 Oct 2007, 20:06, Reply)

Viz insults
My personal fave is from years ago when a character called 'rude kid' retorted to his mother following: "had a nice day in the park darling?"

Piss up a rope twatstick! (complete with middle finger)
(ziderman2001, Tue 9 Oct 2007, 20:02, Reply)