I normally do fondant cakes and don't usually use a border, but I'm doing a white buttercream cake with white scrolls on it as an anniversary gift to my friend. I don't have a clue what type of boder to use at the base! Any ideas what normally go there? TIA!

I like a regular shell border for the base. If there's a top border too, I like the reverse shell.

http://www.wilton.com/technique/Bead
or
http://www.wilton.com/technique/Reverse-Shell

If I'm piping scrolls with a writing tip, I tend to do a bead border. This is similar to a shell border but using a larger writing tip (eg. #8 or #10).