I had another look at the Dice Shop's website - good grief - I must stop this.
There are at least 3 different shapes of D7 which you can buy. There is also a D11...
...and I even found a D2...
...which leads me to wonder how we ever came to invent the coin.
This is wonderful - it gives me hope for the future of human ingenuity, but I really must limit the time I spend looking at this stuff.
One thing I realised, which was pretty obvious really, comes from the fact that it is possible to make a nice, reasonably shallow pyramid based on any regular polygon you wish - thus the double D4 from the previous post is two 4-sided pyramids, base-to-base. The thing I hadn't thought of is that, if you round the corners a bit and make the base circular, you can have dissimilar pyramids base-to-base. Thus a 6-sider on top of a 5 sider will give you a D11, and so on.
That's clever, and potentially useful, but a bit lame compared with regular 100-siders and all that, and if the two pyramids are more than slightly different I think I would be suspicious of the fairness of the die.
That's enough. Have to go and lie down for a bit.