" ¡¡JEY!! ¿¡Quién es el jodido que me puso estas píldoras en mi vaso?! "
(Hey!! Who’s the sonofabitch who put these pills in my glass?!)
[sub](I’m going to Spain, and yes, it’s completely stupid, but my dad has managed to make me totally paranoid, something he is not normally able to do.)[/sub]
*Merde! * ~ As I look down at my shoe… In Paris! 
Can’t remember the Portuguese for this one, but it meant, “Leave me alone or I’ll call the police!”
It was actually in the Berlitz phrasebook, and I did come pretty close to having to utter it. Luckily the drunken teenage soccer hooligans decided we weren’t worth the trouble and left on their own.
I’ve once read the (very useful for every Swedish resident, no matter which citizenship) Swedish translation of “Could you settle the bill, please? I’ve just paid my taxes.”
“Me deixa em paz ou eu chame a polícia!”
Or something like that. I just wanted to show off my knowledge of Portuguese.
-Loopus
Snälla, kan du ta notan? Jag har just betalat (kvar)skatten.
Varsågod!
In Farsi, Arabic, Tagalog, or Spanish (depending where I am):
No, I’m not American. Please don’t shoot me!*
*For the humor impaired: It’s a joke!
In a group of close friends, we have always been unanimous in the usefulness of following German phrases (unfortunately, as of yet we have not had the chance to use any of them):
Ach, Scheisse! Ich habe Sauerkraut in meine Lederhosen.
Mein Panzardivizion ist kaputt.
Ein Kugel, ohne Zahne, bitte.
I personally am using the third one (or similar ones) of auRa’s list quite often, but with the Z replaced by an S.
The other ones I haven’t used yet, fortunately.
These are all phonetic and incorrectly spelled . . . But a translator friend at the CIA once gave them to me:
“Zdravo, mornar, novi u gradu?” (Serbian for “Hello, sailor, new in town?”).
“Mtu sona umbayu. Leka bunduki.” (Swahili for “That man is very ugly. Bring me my gun”).
“Nimi shim pek po ta.” (Korean for “Your mother has a bald pussy”).
In bad Germanese:
Bitte, könnten Sie mir zeigen, wo kann ich mich den Magen ausgepumpt werden, ohne irgendjemanden Fragen zu stellen?
Can you please tell me where I can get my stomach pumped out without anyone asking questions?
Oh, look - a freaky cool link.
Ah crap. Now see what happens when you study German for a few years and then take a break for four years? It all just flows out of your ears. I’m surprised I still remembered to capitalize all the nouns… 
tu madre la mama rico senhor perro tu chupasta la culo de mi gato!
The Lonely Planet French phrasebook includes the phrase for “Where is the nearest methadone clinic?” which I have, regrettably, forgotten.
Something in Hungarian that translates to “My hovercraft is full of eels.”
This post fufills this thread’s Obligatory Monty Python Reference requirement.
from Lodrain’s linked site-
I understand your language perfectly.
" Je parle français comme une vache espagnole. "
heh. heh. heh. <snort>
Niemand erwartet die spanische Inquisition!!!
This post fulfills this thread’s Obligatory Second Monty Python Reference That Really Overdoes It. You may all beat me with sticks.
Or attack you with fresh fruit.
Eso no es mi cocaína, el oficial. (That is not my cocaine, officer)
Sí, ésos son mis intestinos. (Yes, those are my intestines.)
How about “nyet, ya ne chechenka-terroristka”?
(No, I’m not a Chechen terrorist)