The ones listed in the thread were visually great, but the most importantly thing was making the design relevant to what the person's business is about. Here's a few of my favourites:
Some teeth impressions adds a touch of class to this dental business card.
A great idea (plus it's cheap to make too.)
This personal trainer is taking it a little to the extreme, but a brilliant concept.
Ouch.
Check out the full thread here.