A language designed to look like the orthography 5+31230+yp!(@11y used by h4x0rz.
The best-known cellular automaton, which can be used as a form of esoteric programming. It has been shown to be Turing complete. I have seen Life 'programs' that do interesting things, such as adding together two binary numbers, finding prime numbers and even playing Life on a large scale.
Lots Of Lambda Abstractions. A functional tarpit based on lambda calculus.