Ice
In the toilets of the student union building at my university, they regularly put up public service announcement posters to warn the students of all the terrible things that can befall us - depression, gambling addiction, prostate cancer, etc. A few years ago, one poster appeared warning us of the perils of methamphetamine abuse. As can be seen from the link, it featured a haggard looking businessman staring across his desk and wringing his hands, accompanied by the caption "ICE WILL RUIN HIS CAREER, THEN HIS LIFE".

Of course, this poster could hardly go a day without some wag editing it:

MICE WILL RUIN HIS CAREER, THEN HIS LIFE

RICE WILL RUIN HIS CAREER, THEN HIS LIFE

LICE WILL RUIN HIS CAREER, THEN HIS LIFE

These came and went fairly quickly, as I guess the cleaners were scrubbing the graffiti off with alcohol wipes or something. One day, I ducked in for a slash, and the poster had been recently cleaned. As I happened to have a Sharpie in my bag, this was the perfect opportunity to add my own contribution. But what? I racked my brain, and then hit upon the perfect edit. A quick addition to the text and a scrawled on pair of 80s sunglasses later:

MIAMI VICE WILL RUIN HIS CAREER, THEN HIS LIFE


They gave up cleaning it and replaced it with a poster of a depressed footballer instead.
(oball needs Satan more than he needs me, Thu 7 Oct 2010, 14:32, 7 replies)

MAN JUICE WILL RUIN HIS CAREER, THEN HIS LIFE
Others:

THIS ADVICE (very self-referential!)
LICORICE
POLICE
INJUSTICE
ORIFICE
MALPRACTICE
PLAICE

I'm sure B3tards can think of others
(moon monkey is busy making memories worth repressing, Thu 7 Oct 2010, 14:42, closed)

SACRIFICE
seems like an obvious one. Also:

OLD SPICE
(porkinator is a Rock n Roll nerd!, Thu 7 Oct 2010, 14:45, closed)

ANIKA RICE or
SCARY SPICE

will ruin his yadda yadda yadda...
( Colonel Dracula Two manky hookers and a racist dwarf, Thu 7 Oct 2010, 14:49, closed)

OLD SPICE
That is all.

edit: DAMMIT (only just saw above)
(Lythium deals in lead, my friend., Thu 7 Oct 2010, 14:48, closed)

AVARICE
Make it a bit of a moral comment.
(SnowyTheWereRabbit the Leporid from Hell, Thu 7 Oct 2010, 15:04, closed)

These are great
but unfortunately the posters were displayed in a pre-installed plastic frame. You could add another word above, as I did, but there was only really enough room to add one letter before "ice".
(oball needs Satan more than he needs me, Fri 8 Oct 2010, 11:24, closed)

grep ice$ /usr/share/dict/words has a lot to say on the matter
My favourite is dentifrice, or maybe malpractice.
(longbeast mrp, Thu 7 Oct 2010, 17:58, closed)