Moore graph
A graph which achieves the Moore bound. These are complete graphs, polygon graphs (regular graphs of degree 2) and three others: (nodes, degree, diameter) = (10,3,2), (50,7,2) and the possible but undiscovered (3250,57,2).
MegaLexica
A graph which achieves the Moore bound. These are complete graphs, polygon graphs (regular graphs of degree 2) and three others: (nodes, degree, diameter) = (10,3,2), (50,7,2) and the possible but undiscovered (3250,57,2).