How to draw just the arrow tip in TikZ

Question

How can one draw "just the arrow tip" from one of the arrows in the arrow tip library in TikZ?

The problem is that if you try a brute-force solution, eg.

\tikz \draw[-triangle 90] (0,0) -- +(.1,0);

you run into trouble because this produces a small line, the (0,0) to (.1, 0) part, which cannot be removed (a remnant remains no matter if you change .1 to .00001). This is a problem when one wants to rotate the arrow for use in "dropping arrow tips" along a path, as in Andrew Stacey's solution from this question.

Answer 1

\documentclass{minimal}
\usepackage{tikz} 
\usetikzlibrary{arrows}

\begin{document}
\fbox{ \begin{tikzpicture}
\node[inner sep=0pt] {\tikz\draw[-triangle 90](0,0) ;};  
 \end{tikzpicture}} 
\fbox{ \begin{tikzpicture}
\node[rotate=90,inner sep=0pt] {\tikz\draw[-triangle 90](0,0) ;};  
 \end{tikzpicture}  }
\fbox{ \begin{tikzpicture}
\node[rotate=180,inner sep=0pt] {\tikz\draw[-triangle 90](0,0) ;};  
 \end{tikzpicture}  }
\fbox{  \begin{tikzpicture}
\node[rotate=270,inner sep=0pt] {\tikz\draw[-triangle 90](0,0) ;};  
 \end{tikzpicture}  }     

\end{document}

Answer 2

You can use the markings decoration library like so:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{arrows}
\begin{document}
\tikz\path[decoration={markings,mark=at position 1 with \arrow{triangle 90}}, decorate] (0,0);
\end{document}

That won't draw the line, only the arrow. You can change the coordinate to get it elsewhere.

Edit: I see from your comment that your intention with this is to get arrows on a cruved path. That just makes the markings method more useful, since markings can also be used like this:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{arrows}
\begin{document}
  \begin{tikzpicture}
    \path[draw,%
          decoration={%
            markings,%
            mark=at position 0.0   with \arrow{triangle 90},%
            mark=at position 0.5   with \arrow{triangle 90},%
            mark=at position 0.999 with \arrow{triangle 90},% 1 does not work for some reason, not exactly sure why...
          },%
          postaction=decorate] (0,0) to[out=90, in=180] (2,2);
    \node at (3,1) {or};
    \path[xshift=4cm, draw,%
          decoration={%
            markings,%
            mark=between positions 0 and 1 step 5mm with \arrow{triangle 90},%
          },%
          postaction=decorate] (0,0) to[out=90, in=180] (2,2);
    \node at (7,1) {or};
    \path[xshift=8cm, draw,%
          decoration={%
            markings,%
            mark=at position 0   cm with \arrow{triangle 90},%
            mark=at position 0.5 cm with \arrow{triangle 90},%
            mark=at position 1   cm with \arrow{triangle 90},%
            mark=at position 2   cm with \arrow{triangle 90},%
            mark=at position 3   cm with \arrow{triangle 90},%
          },%
          postaction=decorate] (0,0) to[out=90, in=180] (2,2);
  \end{tikzpicture}
\end{document}

Which results in:

As you can see, you can give fractions of the path, there is a step syntax and you can give absolute positions on the path. You can place other things than arrows as well, pretty much anything you can draw with TikZ actually. The following is perfectly valid for instance:

mark=between positions 0 and 1 step 5mm with {\node[draw,circle,fill=blue!20, inner sep=1pt] {x};}