We worked with a great designer (and soon-to-be-groom) to print his dream Save the Date coasters. These played on the idea of 'tying the knot' with a range of layouts of knotted rope.
The reverse of the coaster featured a simple mention of the date and location of the wedding and a custom monogram featuring the initials of the grooms:
The cleverest element of this design was the way in which the coasters can be overlapped to create a single, unified image. Here's a diagram to show how it works: