! (thing) by ariels - Everything2.com

The exclamation mark.
The customary symbol for the factorial operation.
In chess, the symbol for a good move.
"pling" -- The accessor in BBC BASIC for a word (2 bytes). !1234 is the word at address 1234 (decimal; in practice you'd want to use !&4D2). In modern terminology, !x was an lvalue; you could also assign to it.
The boolean negation operator in C (and its many offspring, including C++, Perl, csh, awk etc.).
The shell escape in many UN*X tools, such as vi, ftp, Nethack. ! brings you to a subshell; ! cmd executes cmd.
In Nethack, a potion.

?	Mathematical uniqueness	You cannot blow bubbles with gum arabic	HTML symbol reference
BBC BASIC	Table of ASCII Characters	factorial	The world's shortest correspondence
@		RISC OS	UN*X
cut	obey	NeXTStep	Prolog
ASCII	mind	Unicode European Alphabets	State Opening of Parliament
Acorn Archimedes	conform	Pling