\documentclass[12pt]{article}
\usepackage{graphicx}
\usepackage{tabulary}
\usepackage{rotating}
\begin{document}

\begin{tabular}{|r|c|c|}
\hline
\\ \\ \\ \\ \\ \\ \\ \\ \\ \\
 & \begin{rotate}{45}Trying to save some horizontal space\end{rotate} & \begin{rotate}{45}While keeping headers readable\end{rotate} \\
\hline
this & is & a \\
\hline
sample & latex & table \\
\hline
\end{tabular}
\end{document}