One way is to use `nicematrix`. This avoids the need to add marks in the body of the tabular.
```
\documentclass{beamer}
\usepackage{booktabs}
\usepackage{nicematrix}
\usepackage{tikz}
\usetikzlibrary{tikzmark,overlay-beamer-styles}
\beamertemplatenavigationsymbolsempty
\begin{document}
\begin{frame}
\frametitle{With \texttt{nicematrix}}
\small
\begin{NiceTabular}[code-after={\begin{tikzpicture}
\path (row-6) -- (row-7) coordinate[pos=0.5] (aux);
\draw[red,visible on=<2>]  (aux-|col-1) -- (aux-|col-4);
\end{tikzpicture}}]{lll}
\toprule
\large Subject: & \large Topics & \large Reference \\
\midrule
one & two & three \\
one & two & three \\
one & two & three \\
one & two & three \\
four & five & six \\
one & two & three \\
one & two & three \\
one & two & three \\
\bottomrule
\end{NiceTabular}
\end{frame}
\end{document}
```
![ani.gif](/image?hash=df6d6eab1f69de6febdf2c9b3aef75a9be043fa330e0c4f62ebcdcbfece08b3d)

And here are some basic ways to do that with `tikzmark` (with `\tikzmarknode` specifically, otherwise this is very similar to samcarter's nice answer).

```
\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{tikzmark,overlay-beamer-styles}
\beamertemplatenavigationsymbolsempty
\begin{document}

\begin{frame}
\frametitle{With \texttt{tikzmark}}
\small
\begin{tabular}{|l|l|l|}
\hline
\large Subject: & \large Topics & \large Reference \\
\hline
one & two & three \\
one & two & three \\
one & two & three \\
one & two & three \\
\tikzmarknode{four}{four} & five & \tikzmarknode{six}{six} 
\begin{tikzpicture}[overlay,remember picture]
\draw[red,visible on=<2>] (four.west) -- (six.east|-four);
\end{tikzpicture}\\
one & two & three \\
one & two & three \\
one & two & three \\
\hline
\end{tabular}
\end{frame}

\begin{frame}
\frametitle{With \texttt{tikzmark}}
\small\tikzmark{l}%
\begin{tabular}{|l|l|l|}
\hline
\large Subject: & \large Topics & \large Reference \\
\hline
one & two & three \\
one & two & three \\
one & two & three \\
one & two & three \\
\tikzmarknode{four}{four} & five & \tikzmarknode{six}{six}\\
one & two & three \\
one & two & three \\
one & two & three \\
\hline
\end{tabular}\tikzmark{r}
\begin{tikzpicture}[overlay,remember picture]
\draw[red,visible on=<2>,shorten >=0.2pt,shorten <=0.2pt] (pic cs:l) coordinate (L) 
(pic cs:r) coordinate (R)
(four-|L) -- (four-|R);
\end{tikzpicture}
\end{frame}

\begin{frame}
\frametitle{With \texttt{tikzmark}}
\small\tikzmark{l}%
\begin{tabular}{|l|l|l|}
\hline
\large Subject: & \large Topics & \large Reference \\
\hline
one & two & three \\
one & two & three \\
one & two & three \\
one & two & three \\
\tikzmarknode{four}{four} & five & \tikzmarknode{six}{six}\\
one & two & three \\
one & two & three \\
one & two & three \\
\hline
\end{tabular}\tikzmark{r}
\begin{tikzpicture}[overlay,remember picture]
\draw[red,visible on=<2>,shorten >=0.2pt,shorten <=0.2pt] (pic cs:l) coordinate (L) 
(pic cs:r) coordinate (R)
(four.south-|L) -- (six.north-|R)
(four.south-|R) -- (six.north-|L);
\end{tikzpicture}
\end{frame}
\end{document}
```
![ani.gif](/image?hash=f8a24c88da41e7dcef9ea511e882dc79d99e54bc6b5e52244261970410b08a34)

One approach using `tikzmark` (but please don't make such data-prison-style tables):

```
\documentclass{beamer}
\beamertemplatenavigationsymbolsempty

\usepackage{tikz}
\usetikzlibrary{tikzmark}

\begin{document}

\begin{frame}{}
	\small
\begin{tabular}{|l|l|l|}
\hline
\large Subject: & \large Topics & \large Reference \\
\hline
one & two & three \\
one & two & three \\
one & two & three \\
one & two & three \\
\tikzmark{aaa}four & five & six \tikzmark{bbb} \\
one & two & three \\
one & two & three \\
one & two & three \\
\hline
\end{tabular}

\begin{tikzpicture}[remember picture,overlay]
\draw ([yshift=0.8ex]pic cs:aaa) -- ([yshift=0.8ex]pic cs:bbb);
\end{tikzpicture}

\end{frame}

\end{document}
```

![Screen Shot 2020-10-02 at 21.32.01.png](/image?hash=fdf7e2b0731bfd3a7e15f21359b7685e27e4ca6c8403c375047e869bb1b7dd1d)

One can achieve this effect by placing a shifted `\hline`.

Caveat: This only gives the correct placement for the simplest case, the previous line contains nothing bigger than an `\@arstrut` (so normal text works). For anything else one would have to make some measurements, and hence the solutions using `nicematrix` or `tikzmark`s are generally preferable (this answer has the advantage of being faster and needing only a single pass).

```
\documentclass{beamer}
\beamertemplatenavigationsymbolsempty

\makeatletter
\newcommand\strikeoutprevrow
  {%
    \noalign
      {%
        \vskip-.5\dimexpr\ht\@arstrutbox+\dp\@arstrutbox+\arrayrulewidth\relax
        \hrule\@height\arrayrulewidth
        \vskip.5\dimexpr\ht\@arstrutbox+\dp\@arstrutbox-\arrayrulewidth\relax
      }%
  }
\makeatother

\begin{document}

\begin{frame}{}
	\small
\begin{tabular}{|l|l|l|}
\hline
\large Subject: & \large Topics & \large Reference \\
\hline
one & two & three \\
one & two & three \\
one & two & three \\
one & two & three \\
four & five & six \\
\strikeoutprevrow
one & two & three \\
one & two & three \\
one & two & three \\
\hline
\end{tabular}
\end{frame}

\end{document}
```

![crossouttablerow-1.png](/image?hash=977970482469a4c905431de7baa6f1a5348996c45afe44be35e94bd0df9c8c56)

Here is a solution with recent versions of `nicematrix` (the code is shorter than with other solutions which were using older versions of `nicematrix`).

    \documentclass{beamer}
    \usepackage{booktabs}
    \usepackage{nicematrix}
    \usepackage{tikz}
    \usetikzlibrary{overlay-beamer-styles}
    \beamertemplatenavigationsymbolsempty
    \begin{document}
    \begin{frame}
    \frametitle{With \texttt{nicematrix}}
    \small
    \begin{NiceTabular}{lll}
    \toprule
    \large Subject: & \large Topics & \large Reference \\
    \midrule
    one & two & three \\
    one & two & three \\
    one & two & three \\
    one & two & three \\
    four & five & six \\
    one & two & three \\
    one & two & three \\
    one & two & three \\
    \bottomrule
    \CodeAfter
       \tikz \draw [thick,red,visible on=<2>]  (6.5-|1) -- (6.5-|4) ;
    \end{NiceTabular}
    \end{frame}
    \end{document}