Also a name David Langford gave to images whose mere seeing might cause damage in human brain. Any basilisks are not known to exist, but in theory they could be possible. From comp.basilisk FAQ:

He imagined the human mind as a formal, deterministic computational system - a system that, as predicted by a variant of Gödel's Theorem in mathematics, can be crashed by thoughts that the mind is physically or logically incapable of thinking. The Logical Imaging Technique presents such a thought in purely visual form as a basilisk image which our optic nerves can't help but accept. The result is disastrous, like a software stealth-virus smuggled into the brain.

Some basilisk-related appearances in fiction:

source: comp.basilisk FAQ,, except for the babylon 5 part =)