I have an intellectual crush on Douglas Hofstadter, and amongst things I have learnt from him and experimented with, are ambigrams.

AotD

The following is one I designed for a friend that ended up tattooed on his arm.

This stands for AOTD, an acronym for "All Of The Day". That is a phrase that my friend and his significant one found to be meaningful. The design is nice because it can be read as you see it, as well as upside-down. Thus the happy couple can see the same thing, while looking at it each from their own perspective. Such is love.

Abbey theatre medal

This medal was designed for the Abbey Theatre in Dublin. It made it to the finals of a contest with over 30 design and art students participating.The concept behind it is expressed through the use of an ambigram. 

Ambigrams are words that can be read in different ways (here the words "Abbey Theatre can be read both vertically and horizontally). Inspired by the duplicity of theatre (the persons and the mask), this medal is simple yet conveys a high level of complexity.The ‘A’ from the Abbey Theatre logo is used as a guide the viewer to the reading of both messages. In a second version of the medal, the words can be read whether the medal is upside-down or not.