the Berry Paradox
“Berry's paradox involves describing something using a description whose form is in apparent contradiction with the meaning of the description.” (Peter H. Roosen-Runge)
“The first number not nameable in under ten words”
Gregory Chaitin in Complexity 1:1 (1995), pp. 26-30 http://www.cs.auckland.ac.nz/CDMTCS/chaitin/unm2.html