The Living Thing / Notebooks :

Models of computation

Turing machines, λ-calculus, term-rewriting and other models of what may be computed.

Everything is Turing-complete

Surprsingly Turing Complete

Many configuration or special-purpose languages or tools or complicated games turn out to violate the Rule of least power & be “accidentally Turing-complete”, like MediaWiki templates, sed or repeated regexp/find-replace commands in an editor (any form of string substitution or templating or compile-time computation is highly likely to be TC on its own or when iterated since they often turn out to support a lambda calculus or a term-rewriting language or tag system eg esolangs “///” or Thue ), XSLT, Infinite Minesweeper, Dwarf Fortress3, Starcraft, Minecraft, Ant, Transport Tycoon, C++ templates & Java generics, DNA computing etc are TC but these are not surprising … On the other hand, the vein of computer security research called “weird machines” is a fertile ground of “that’s TC?” reactions. What is “surprising” may differ from person to person.

Weird stuff

John Shutt’s weird λ-calculus-based approaches to superunification:

A more straightforward solution, […] is to give up on chronological
determinism and instead acquire mathematical determinism, by the arguably
“obvious” strategy of supposing that the whole of spacetime evolves
deterministically along an orthogonal dimension, converting unknown initial
conditions (initial in the orthogonal dimension) into chronological
nondeterminism. […]

The approach does, however, seem well-suited to a co-hygiene-directed theory.
Church-Rosser-ness implies that term rewriting should be treated as reasoning
rather than directly as chronological evolution, which seemingly puts term
rewriting on a dimension orthogonal to spacetime.
The earlier co-hygiene post noted that calculi, which converge to an answer
via Church-Rosser-ness, contrast with grammars, which are also term-rewriting
systems but exist for the purpose of diverging and are thus naturally allied
with mathematical nondeterminism whereas calculi naturally ally with
mathematical determinism.
So our desire to exploit the calculus/physics analogy, together with our
desire for abstract separability of parts, seems to favor this use of a
rewriting dimension orthogonal to spacetime.

I bet Hackernews weighs in over-enthusiastically on this.

Rewriting Systems

Especially string rewriting but you can do almost-anything rewriting.