\documentclass{article}
\usepackage{tikz}
\usepackage[francais,bloc]{automultiplechoice}

\begin{document}

\exemplaire{2}{
\makeatletter
\pgfmathsetseed{123321}

\def\prunelist##1{%
\expandafter\edef\csname pgfmath@randomlist@##1\endcsname
        {\the\numexpr\csname pgfmath@randomlist@##1\endcsname-1\relax}
\count@\pgfmath@randomtemp 
\loop
\expandafter\let
\csname pgfmath@randomlist@##1@\the\count@\expandafter\endcsname
\csname pgfmath@randomlist@##1@\the\numexpr\count@+1\relax\endcsname
\ifnum\count@<\csname pgfmath@randomlist@##1\endcsname\relax
\advance\count@\@ne
\repeat
}

\pgfmathdeclarerandomlist{mylist}{{one}{two}{three}{four}{five}{six}{seven}}

\pgfmathrandomitem\z{mylist}\z\prunelist{mylist}

}
\end{document}