A famous case of self citation was by Prof. Dr.-Ing. W.-M. Kulicke from Institute for Technical and Macromolecular Chemistry, University of Hamburg. The case was published in Annals of Improbable Research Vol. 12 (2006) Issue 4.
Werner-Michael Kulicke’s paper : “Rheo-Optical and Rheo-Mechanical Characterization of the Viscoelastic Properties and Shear-Induced Orientation of Hydrocolloids,” C. Clasen and W.-M. Kulicke, Proceedings of the 2nd International Symposium on Food Rheology, and Structure, 2000, pp. 25–33.
Kulicke cites 23 times to his own work out of a total of 29 references — so 80 percent are his own!
In another conference paper: “Characterization of water-soluble cellulose derivatives in terms of the molar mass and particle size as well as their distribution” by Kulicke, W.-M., Clasen, C., Lohman, C., Macromolecular Symposia Volume 223, March 2005, Pages 151-174. Kulicke cited 21 times to his own work out of a total of 44 references, almost 50%.