That's all personal choice really.
Here's a list of font sites to find a free cool font
Fonts by theme
ddfont
Better Fonts
Search free fonts
Dafont
Font space
ffonts
Stencil Revolution
Font temple
Simply the best
Urban fonts
Search free fonts
Fonts 500
Fonts 101
Font in need
1001 fonts
Free fonts
Daily free fonts
ufonts
Font Yukle
Font Squirrel
Abstract fonts
Font zone
Fonts2u
Then it's just trial and error. Some fonts that look cool don't look very good when they are small enough for ranks. You just have to try them and see..
I hope this list helps.