Print every character your program doesn't have
Polyglot, 95

#undef X;A!"$%&amp;'()*+-[,.]/0123456789:&lt;=&gt;?@BCDEFGHIJKLMNOPQRSTUVWYZ\^_`abcghijklmopqrstvwxyz{|}~



Perl
Perl 6
Any *nx-like shell (tclsh, bash, sh, ksh, etc)
Awk (GNU / POSIX)
Brainfuck, Brian &amp; Chuck, other derivatives
Ruby
Coffescript
Golfscript
Python
R
Julia
Whitespace
rk
Gaot++
bc
jq
Joy
Tcl
99
V (FMota)
Acc!!
C - if no main() is needed. Thanks to urogen
Probably more.


Does nothing.