2 times the character
2 times the character ®
2 times the character ¯
2 times the character »
2 times the character Ø
I would be using some of those fancy Unicode characters from some time now if I wasn't afraid that applications weren't able to handle them properly, thus locking myself out of websites. Coping with Unicode is hard.
Off the top of my head, and easily type'able with my actual keyboard setup/layout: « » ß þ Þ æ Æ ø Ø