A solution with booktabs as vertical lines are distracting the reader. If you need them, just use my snippet below with |l|l| and normal \hline and \cline{1-1} commands.
% arara: pdflatex
\documentclass{article}
\usepackage{booktabs} % my recommendation. Used in first and second version
\usepackage{multirow} % just for the second and third version
\usepackage{caption} % optional for nicer vertical spacing
\begin{document}
\begin{table}%
\caption{Your Table}
\centering
\begin{tabular}{ll}
\toprule
top left&right\\
\cmidrule(r){1-1}
bottom left&\\
\bottomrule
\end{tabular}
\end{table}
\begin{table}%
\caption{Your Table with Centered Right Side}
\centering
\begin{tabular}{ll}
\toprule
top left&\multirow{2}{*}{centered right}\\
\cmidrule(r){1-1}
bottom left&\\
\bottomrule
\end{tabular}
\end{table}
\begin{table}%
\caption{Your Table with Vertical Lines}
\centering
\begin{tabular}{|l|l|}
\hline
top left&\multirow{2}{*}{centered right}\\
\cline{1-1}
bottom left&\\
\hline
\end{tabular}
\end{table}
\end{document}
The (r) is optional. Have a look, if you like it more without this constraint.
