\documentclass{article}
\usepackage{tikz}
\newcommand\drawline[1][black]{%
\begin{tikzpicture}
\draw[#1] (0pt,0pt) -- (15pt,0pt);
\end{tikzpicture}%
}
%\newcommand\drawline[1]{%
% \begin{tikzpicture}
% \draw[#1] (0pt,0pt) -- (15pt,0pt);
% \end{tikzpicture}%
%}
\begin{document}
\listoffigures
\begin{figure}
\caption{test \drawline[ultra thick]}
%\caption{test \drawline{ultra thick}}
\end{figure}
\end{document}