\begin{equation}
    \left\{
        \begin{aligned}
            lhs1 &= rhs1 \\
            lhs2 &= rhs2 \\
        \end{aligned}
    \right.
\end{equation}

\left]a,b\right[
\bigl]a,b\bigr]
\Bigl]a,b\Bigr]
\biggl]a,b\biggr]
\Biggl]a,b\Biggr]

\left( \frac{a}{b} \middle| q \right)

    \begin{tabular}{@{} lr @{}}
      \toprule
      City & Population\\
      \midrule
      Mexico City & 20,116,842\\
      Shanghai & 19,210,000\\
      Peking & 15,796,450\\
      Istanbul & 14,160,467\\
      \bottomrule
    \end{tabular}

\begin{itemize}
\item
...
\item
\end{itemize}

\ifpdf
\DeclareGraphicsExtensions{.pdf,.jpg,.png}
\else
\DeclareGraphicsExtensions{.eps,.jpg,.png}
\fi

\makeatletter
\makeatother
\begingroup ...\endgroup