improve a graph

Question

I have the following code for a figure. I'm not satisfied with the result, in particular "the bullet". How improve this figure ? Thanks

  \def\xmin{-5}\def\xmax{5}
  \def\ymin{-1.5}\def\ymax{1.5}
\begin{tikzpicture}[scale=1.5]
    \draw[dotted,step=1] (\xmin,\ymin) grid (\xmax,\ymax);
    \draw[thick, ->] (\xmin,0)--(\xmax,0);
    \draw[thick, ->] (0,\ymin)--(0,\ymax);
    \clip (\xmin,\ymin) rectangle (\xmax,\ymax);
    \foreach \i in {-2,...,2}{
      \draw[very thick, *-(] (2\i-1,-.5)--(2\i+1,.5);
    }
  \end{tikzpicture}