\1

This once used to be my signature on the comp.unix.shell newsgroup (warning: may not work with some implementations of sed):

Copy and distribution of the code published in this page, with or without
modification, are permitted in any medium without royalty provided the copyright
notice (see bottom of page) and this notice are preserved.

echo 0|sed 's909=mO#3u)o19;s0#0co*)].O0;s()(0bu}=(;s#}#m1$"?0^2{#;
s)")9v2@3%"9$);s[%[o]x(.$e#![;sz(z^+.z;su+ur!z"au;sxzxd?_{g)/x;:b;
s/\(\(.\).\)\(\(..\)*\)\(\(.\).\)\(\(..\)*#.*\6.*\2.*\)/\5\3\1\7/;
tb'|awk '{while((i+=2)<=length($1)-24)a=a substr($1,i,1);print a}'

What it does is to print (one of) my email address, but in a (hopefully) spambot-unfriendly way.