Mandlebrot flythrough is my personal favorite: http://www.perlmonks.org/?node_id=329492

See the more recent Acme::EyeDrops : https://metacpan.org/module/Acme::EyeDrops

I've always liked http://www.cise.ufl.edu/~manuel/obfuscate/piglatin as well.

It seems like it would be trivial to arrange nearly any non-whitespace-significant language into arbitrary ASCII art.