Favorite key: The John Key http://en.wikipedia.org/wiki/John_Key
Least Favorite Key: Scroll lock (wtf does it do anyway?)

What's your's lovely-dovelies?

Scroll lock for me too. What does it actually do?

Well, judging by the amount of grip that has been rubbed off my keys, the Shift key is my favorite.

As for my least favorite it's the Insert key. I never use that thing.

Dommyboy:
Scroll lock for me too. What does it actually do?

Maybe it opens THE FIERY GATES OF HELL! or jacks you off. Never really pressed it.

I love pressing any and all buttons on my lap-top. They feel really nice to tap for some reason...

I don't like how the 'Home' button is so close to the Backspace button though. Sometimes I'm deleting letters and then I suddenly switch to deleting paragraphs.

EDIT:
Or Sticky Keys. That counts, right? I hate it when I'm playing TF2 and I start pressing crouch because I'm bored waiting for the game to start - the game crashes and windows asks if anything's wrong because I pressed shift too many times in a row. It's annoying and I keep forgetting about it when I'm playing a game.

I hate the ins key.

As for my favorite, I think I have to go with shift+` because it makes a ~ which looks pretty cool.

I personally hate the "home" key because it's right next to backspace on my laptop, so sometimes I'll hit it instead of backspace, and end up typing the next two words at the beginning of the line I already typed instead of backspacing and moving on.

The '~' is actually called the 'Tilde' key. What does it mean? *says in cheesy ghost voice* Nooooboody knooooows

Well my least favourite key was going to be the microsoft windows start bar key thingy. Back before games would lock it out to stop you from accidently pressing mid fight I developed a deep hatred for it. The insert key annoys me from time to time when it accidently gets pressed and when I edit some writing it overwrites rather then adds.
But now that you mention it, a New Zealand key would make my least fav.

My favourite would be the treble clef. So sexy.

And Scroll Lock is used mainly on forms and data entry into spreadsheets and the like. What it does is switch the arrow keys from moving the text input bar thing, changing it to moving the focus between fields.
Open up excel and give it a go.
Tilde is used in programming from what I remember, been a while. Also can be used to add a bit of emphasis to a certain word to make it drag on and out I believe. Like helloooooooo could be changed to hello~ and it represents the dragging of the word and fades out...but all that part is just a guess :P
Gogo wiki.

xitel:
Well, judging by the amount of grip that has been rubbed off my keys, the Shift key is my favorite.

As for my least favorite it's the Insert key. I never use that thing.

That thing pisses me off soo much. When I accidentally hit it and mess up anything I'm writing.

My favourite is the ~, I like it because in most games it opens up a screen with code; good for simple hacks.

My favourite key is a tie between Enter and Space. MY least favourite is definitely the ';' key... I always hit it when I mean to hit the ' key.

My favorite key is the Ctrl key; there's so many things you can do with it!

Least favorite would be the Windows key. I hate trying to press Ctrl to crouch, and press Windows instead, launching me to my desktop. D=

I have a love/hate relationship with the windows key. i like it because a lot if commands are hotkeyed to it. but its annoying in games because ill go to crouch and then i lag out because my start menu gets pulled up

Spacebar, because I use it for Jump. ^o^

Spacebar, because it's always the first one to get stuck & need cleaning >.<

My favorite key is the Enter I think, I like slamming down on it after I've written a long and good line of text somewhere, or when launching a program. (It's more reliable than double-clicking on a slow PC like mine.)
My least favorite key is the Caps Lock. I virtually never use it, but sometimes press it by ACCIDENT AND SUDDENLY TYPE LIKE THIS.

Whatever key controlled the OVER function in Word. I'm fairly sure it was Insert, Home or End as it would switch on during editing.

MY FAVORITE WOULD BE THIS ONE... MAINLY FOR HILARIOUS "WHY ARE YOU SHOUTING AT ME" RESPONSES.

Puppeteer Putin:
MY FAVORITE WOULD BE THIS ONE... MAINLY FOR HILARIOUS "WHY ARE YOU SHOUTING AT ME" RESPONSES.

Why are you shouting at me? =D

The scroll lock key is useless on modern operating systems as far as I can tell. However, if you're using DOS and it's displaying more than a page's worth of information and scrolling down through such information, you can hit scroll lock to lock the text in place until you are done reading said text.
The advent of scroll bars make the scroll lock key useless unless you want to turn an LED on and off. It does change something in Excel, however.

As for my favorite key, the tilde is nice. Also, I hate any key that brings up a help menu (F1 on PCs and the actual Help button on Macs which is just over an inch away from the delete or backspace button.)

I hate the power button which "Genius" decided would be a great idea to have right next to the enter key........ yeah... yeah i can see why that would be helpful, if you're not experienced with keyboards and turn off your pc at night time that, that would be wonderful.

my favourite key: G16 down here on the bottom left, closely followed by the G18. (Ctrl-C and Ctrl-V macro)
My Least: Ins - it always manages to get effing bumped and make me scramble to correct it's insane shenanigans.

My favorite is actually on a typewriter: shift lock. It's exactly what you'd think it is: a double for caps lock, plus it allows you to hit, say, ~!@#$%^&*(){}|:"<>? without holding shift the whole time. Why has this brilliant innovation not found its way to computers yet?!

My least favorite, by arbitrary (read "flawed") reasoning, is the ; and : key, because I've now used five times in this short post, and that's just wrong.

Gotta love the space bar! I hate the extra "-" you get on the number keypad. Why do you need 2?

ExplosionProofTaco:
Favorite key: The John Key http://en.wikipedia.org/wiki/John_Key
Least Favorite Key: Scroll lock (wtf does it do anyway?)

What's your's lovely-dovelies?

I like the ENTER or RETURN key. It's big, it's punchy, you can really smash it and it always satisfies.

I do not like WINDOWS key - it muscled it's way into keyboards (like we would notice the gap had gone).
I also do not like ' ` ¬ ' - illustrates my point, how do you get the third character and what are they for.
I don't mind Sys Rq but what does it do? I only ever use it to print screen. Maybe i'm missing out on some good stuff.

favourite is probably enter :)))))

least fave has to be shift (for reasons of sticky keys)

Personally, I enjoy my caps lock key quite a lot, especially when I'm feeling extra-silly.
YOU SEE IF YOU IGNORE COMMAS AND PROPER GRAMMAR AND SUCH IT MAKES IT LOOK LIKE YOU HAVE NO INSIDE VOICE AND ALSO ARE A KNOB
...I have a love/hate with the Windows key, too. I use it a lot on purpose to get out of games and go check stuff, but I used to hit it on accident ALL THE TIME. So much anger.
"Our base is under attack!"
"OH FUCK OH SHIT NO OH HELL CRAP DAMN DAMN DAMN"
*Tries to bind a group of people to control+1*
*Is sent to desktop*
"NNNNNNOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO"
But I don't really hate a key. Except maybe trying to use "q" and "z" in quick conversation. Not my idea of fun.

Solo508:
Gotta love the space bar! I hate the extra "-" you get on the number keypad. Why do you need 2?

windows calculator
54556-4524 without moving the hand across

need i say more?

I like my "E" key. It's near "R" "S" and "A", all of which are important keys.

My least favorite key is the " ` " and " ~ " key (next to 1), it just seems useless.

I have a media keyboard with shed loads of extra buttons i never really use. I would but they dont work outside media player whihc doesnt work when mircosoft knows your running a copy.

favorite:shift, least fav:Esc

Reaperman Wompa:
I like my "E" key. It's near "R" "S" and "A", all of which are important keys.

And where would we be without a word like "eraser"? I shudder to think.

Favourite: Space bar...I mean come on...how much would it suck if the space bar was small.

Least Favourite: OBVIOUSLY the windows key...the number of times i've tried to hit CTRL or SHIFT and ended up closing or crashing the game...just THINKING about it makes me want to throw my GF's laptop out the freakin' window.

Favourite= H because it starts off all the conversations.
Least Favourite= The other numpad, don't use it.

Favourite: Enter key. Execute command line programs, one line forward in text documents, et cetera. Just a very useful key in general.

Least favourite: Windows/Menu key. Although I don't have the problems with it that some people do, using Shift as my crouch key, it's merely another way of pressing C-ESC, and that makes it redundant. Also, it's mostly useless in Linux without reconfiguration, which is why my next keyboard will be one of these: http://pckeyboards.stores.yahoo.net/cu104ps2.html. 103 keys, no redundant menu and Windows keys, perfect layout for UK English.