[0123456789abcdef]

There are only 16 characters to work with, but programmers just love coming up with creative spellings using hex numbers. I suspect that leetspeak evolved out of these spellings, though personally I prefer the original form. I assume that everyone working as a software developer in English will have seen 0xdeadbeef, and probably some other favorites as well.
deadbeef	old standby #1
feedf00d	old standby #2
feedface	old standby #3
decafbad	developers love to complain about coffee
badcafe	developers really love to complain about coffee
badc0ffee	developers really, really love to complain about coffee
badc0c0a	MacOS X developers might find more meaning in this one.
c0c0abad	People who hate MacOS X developers might find more meaning in this one.
A little sed scripting on /usr/share/dist/words can turn up a lot of interesting combinations. For the edification and bemusement of the Gentle Reader, allow me to present a few of them here. I rejected most of the results where '5' replaced an 'S' as being too ugly, but a few passed muster. cat /usr/share/dict/words | sed \ -e "s/nine/9/g" -e "s/eight/8/g" -e "s/seven/7/g" -e "s/six/6/g" \ -e "s/five/5/g" -e "s/four/4/g" -e "s/three/3/g" -e "s/two/2/g" \ -e "s/one/1/g" -e "s/zero/0/g" \ -e "s/ated/8ed/g" -e "s/[oO]/0/g" -e "s/[lL]/1/g" -e "s/[sS]/5/g" \ | egrep -v "[^0123456789aAbBcCdDeEfF]" The first few seem particularly suitable for memory fenceposts, either guard words before and after allocations or patterns to scribble over freed memory when looking for use-after-free bugs.
a110c8ed	This memory is in use, buster!
5eef3712	This is ~(0xa110c8ed). No, it doesn't spell anything nifty.
dea110c8	Scribble over memory after free(), to catch dangling references.
defec8ed	to crap all over memory
defaced	another bit pattern to scribble over memory to catch use-after-free errors
To express one's true feelings about the quality of the code base there are really only two options: Profanity-laden comment blocks Clever use of constants
c0defaded	It is a well known fact that old code suffers bit rot. Refactor often!
badfacade	There are times when bad code can only be papered over. This is one of those times.
efface	Good code doesn't make a spectacle of itself.
deface	Bad code, on the other hand, gets drunk at its best friends wedding and hits on the bride.
decade	This code base has been under development for a long time.
baddeed	The EULA for this product specifies the precise amount of bad karma accumulated by using it.
acceded	The software has finally given in.
befa11	As in "what has befallen yon dead process?"
c0dedbad	self explanatory
Magic numbers are useful in all sorts of situations. Encoding one's birthday (0xMMDDYYYY) is clever, but obscure. Subtle jokes in hex also work well.
abbacadabba	Unfortunately 44 bits won't magically fit into a uint32_t.
abadabba dabbadabba abbadabbadabba	Said the monkey to the chimp. Real magic numbers are 128 bit.
d00bee	Debugging probably qualifies as "medicinal purposes."
d0dec0de	How does one pronounce ioctl anyway? "eye oh cottle," or "eye oct all ?"
babe2bed	The kid's bedtime is 7pm sharp.
b0cceba11	You know, I only discovered Bocce Ball in my 30s.
5ca1ab1e	Ignore what you see elsewhere, the secret to scalability is in using good magic numbers.
0x1de	With the leading 0x it sortof looks like "oxide" ... I admit it, this one sucks.
Why should return codes be boring? {0, 1, 2, ...} is so dull. We can do better.
cab0b	yummy
fa1afe1	even more yummy!
b1abbed	probably I/O related
bedded	The code went to sleep?
b0bbed	They call it "floating point" for a reason, bub.
beaded	Um, yeah. I can't think of anything funny about this one.
bab00	My sweet baboo!
10aded	I bet it has an itchy trigger finger, too.
ba11ad	I structure all my code to iambic pentameter.
a100f	My code doesn't like me.
acc01ade	Programmers rarely, if ever, hear praise of their work.
affab1e	Relatively approachable and friendly code, I guess.
babb1e	Why yes, my functions tend to be a bit on the longish side. Why?
baff1e	Why yes, my functions tend to be a bit on the complex side. Why?
babe1	You can write FORTRAN in any language.
ba1b0a	Its the Eye of the Tiger, baby!
ed1f1ce	large, imposing blocks of code
5eceded	This module has declared its independence from the rest of the system.
5c01ded	At times, it is necessary to be stern with the codebase. Give it a time out.
5caff01d	This code was intended to be temporary. That was four years ago. Such is the way of things.
ad0be	I bet they use this one in Photoshop.
ab0de	my humble abode
d8edbabe	In college, yeah, sure you did.
0ddba11	That is a strange one, alright.
Finally, here are some 16 bit numbers which are more interesting than "dead," "f00d" and "beef"
caca	A statement about software quality, I suppose.
deaf	When programming, no-one can hear you scream.
c0ed	It is the 21st century, after all.
ba1d	If tires can go bald, why not programs?
a1fa	I couldn't find a reasonable approximation of beta.
f01d	Origami programming!
fa11	If code falls in the forest, does it make a sound?
c01d	Software is a dish best served cold.
ab1e	Or ! 0xab1e, as the case may be.
cede	I give up, I'm done.
Do you have any additional hex numbers to share? The comments section is open for business.

Update: Lisa Simone wrote an article about teaching embedded systems and the use of hex words in an article on her site.