The Kittell graph is a planar graph on 23 nodes and 63 edges that tangles the Kempe chains in Kempe's coloring algorithm and thus provides an example of how Kempe's (1879) supposed proof of the four-color theorem fails.
The Kittell graph is implemented in the Wolfram Language as GraphData["KittellGraph"].
It is also an identity graph.
The Fritsch graph and Soifer graph provide smaller (and in fact the smallest possible) counterexamples.