craftgrrl | Pens for writing on wood...

Hello, craftypeoples!

I was wondering if anyone had any idea of a good type/brand of pen that can be used to write on wood without bleeding, and preferably permanent. I've been scouring the Internet and I also checked the tags here, and didn't find any suggestions, so I figured I'd ask.

My friend is having a wooden puzzle at her wedding with a pic of her and her hubby on it, and guests can sign the back of the pieces, but we need pens that will work properly on the wood without making too much mess or making the writing illegible. Also I don't think she intends to seal the backs of the pieces after the writing is completed, so permanent would be pretty great.

Any ideas are greatly appreciated!

Thanks!!!