Very slight discontinuities in table borders

This is fixed with the use of the array package:

\documentclass{article}
\usepackage{array}
\begin{document}
  \begin{tabular}{|c|c|}
    \hline
    A & B \\ 
    \hline
    C & D \\ 
    \hline
    E & F \\
    \hline
    G & H \\
    \hline
  \end{tabular}
\end{document}

This is mentioned in the array package documentation:

Please pardon me for channeling my inner booktabs evangelist:

\documentclass{article}
\usepackage{booktabs}

\begin{document}
  \begin{tabular}{cc}
    \toprule
    A & B \\ 
    \midrule
    C & D \\ 
    E & F \\
    G & H \\
    \bottomrule
  \end{tabular}
\end{document}

You might not think much of the difference with this small table, but when looking at a larger and/or more complex table it is much easier for your eyes to examine the data/contents without being distracted by lines everywhere.

You might find some other pointers in an excellent animated GIF created by Darkhorse Analytics: How to make your tables less terrible (Reddit's title, not my judgment of your table... :~) )