There are a lot of you already close to their ten numbers. Maybe We will have a winner today =)
11)
Rene Descartes
Rene Descartes was born on 31st March 1596 in La Haye en Touraine, France and was a French philosopher and mathematician.
So here is a philosophy-fact, because it's far more known than his mathematical achievements.
"Cogito ego sum" - "I think, therefore I am"
The long version of this is, that Descartes principle is the following: Thought exists.
I cannot be separated from my thoughts, therefor, I exists.
So I can conclude:
If I doubt my existence, something in me must "do the doubting", that's the thinking-part, and because I need to think to doubt my existence, I think and therefore I exist.
This actually means that I just proofed my own existence by doubting it
He did a lot of that freaky thinking stuff
Very good for confusing other people
19)
Felix Klein
Felix Klein was born on 25th April 1849 in Düsseldorf, Germany and was a German mathematician. (Another German......)
He did a lot of work in geometry and helped the University of Göttingen (Germany) to become a capital of mathematics, which it was for a long time (I think there is still a lot of maths going on there, I was thinking about changing university and this was among the universities I thought about)
What is most known is the "Klein Bottle", a bottle where you can not tell inside and outside apart. Like the Möbius strip, it has one surface.
(Image is again from Wikipedia)
You can actually get a Klein Bottle from two Möbius strip, you just have to glue the edges together (mathematically seen).
There is a lot of geeky stuff about the bottle, for example you can get a "Klein Bottle Winebottle", a Klein Bottle and you can put wine in there
And there are hats in the shape of this bottle, they go perfectly with a Möbius scarf
Both today. So 7/10. I bet we have a winner tomorrow as it seems several are at 8 or 9. Good luck. 
