[QUOTE=GorillaMan]
Not least because ‘pound key’ for us sounds like you mean shift+3 on a UK-layout keyboard, producing ‘£’ 
[/QUOTE]
And on a US keyboard, shift+3 is “#”, so we have to resort to more desperate measures to produce “£”.
[QUOTE=Lunar Saltlick]
Pound key actually seems to be used more and more often, contrary to what I think the OP is suggesting…
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No, I was saying that “pound key” is IMHO the standard name for the key and I’m always surprised when people don’t recognize that key as the “pound key.”
[QUOTE=Giles]
And on a US keyboard, shift+3 is “#”, so we have to resort to more desperate measures to produce “£”.
[/QUOTE]
And to rub salt into this very minor wound, we don’t need shift to produce a hash symbol.
[QUOTE=Hampshire]
What else would you call the # key besides the pound key?
The * key I usually hear refered to as the star key but I guess you could call it the asterisk key.
[/QUOTE]
The hash key.
There were a few years after we had a rotary phone before we ever needed to touch the “pound key”. I vaguely thought it was there as a place holder or to provide symetry.
I do distinctly recall a discussion about an automated phone call at a diner in the 80s. “And then it said ‘Press the pound key!’ What’s the pound key???” The answer was that it’s the one that looks like the side of Archie’s head.
We had always called # “the number sign” before that.
The star key keeps showing something like this:
------> *
no matter how hard I pound it 
[QUOTE=Hampshire]
What else would you call the # key besides the pound key?
[/QUOTE]
The sharp key?
Pound key is standard here, at least. That’s all I evver hear or say.
Hash I’d understand.
Number key would confuse me because phones generally have ten number keys, and that ain’t one of them.
[QUOTE=tdn]
The sharp key?
[/QUOTE]
No, no, no. A sharp sign has slanted horizontal strokes, and a pound (or hash or octothorpe) has slanted vertical strokes.
Pound sign: #
Sharp sign: ♯
[QUOTE=friedo]
…slanted horizontal… …slanted vertical…
[/QUOTE]
My head is spinning trying to visualise these 
[QUOTE=friedo]
No, no, no. A sharp sign has slanted horizontal strokes, and a pound (or hash or octothorpe) has slanted vertical strokes.
Pound sign: #
Sharp sign: ♯
[/QUOTE]
So give your phone a ten degree counter-clockwise turn.
[QUOTE=susan]
In medical settings, “#” is used for pounds (in the US, at least). As in, “Weight down 5#.”
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Right. THAT, I think, is where the knowledge gap lies. “Everyone” knows it’s called a “pound key”, but I think very few people know that “#” means “pound”, as in, 16 ounces. My mom used to separate and freeze ground beef with the date and “1#” written on it. These days, non-medical people know and use “lb.” instead. I don’t know what happened to change that.
[QUOTE=WhyNot]
These days, non-medical people know and use “lb.” instead. I don’t know what happened to change that.
[/QUOTE]
British English has always used ‘lb’.
I used to call a vendor for support in my previous job and their voice mail system had a pleasant woman’s voice with a British accent that would direct me to enter the extension I wanted to dial, followed by the “hash” key.
I’d call # the pound key, but if I were speaking to someone from the UK, I’d know what else I could call it.
[QUOTE=GorillaMan]
British English has always used ‘lb’.
[/QUOTE]
Yes indeed.
British Telecom (I used to work for them) calls # the hash key.
I haven’t done a scientific study, but I’d say in Canada you’re more likely to hear someone say “Press the number sign”. I’m no kid, and I never saw anyone in Canada use “#” instead of “lb”. (Back in the old pre-metric days).
Hash key here in the UK< obviously because ‘pound symbol’ means something else (currency)
I’m familiar with pound key, but I’ve also heard number sign. In French the most common term is le carré (the square), but I’ve also heard le dièse (the sharp sign). My terminology references give pound and carré as the official terms.
Never heard it called anything but the hash key here in Aus. I think I used to know that # was shorthand for pound but it’s certainly not in common use here. (We never need to use “pounds” since we have dollars and kilograms instead)
A previous example of a cultural clash regarding the hash/pound sign.