Is there a "contradiction" symbol in some font, somewhere?

My attempt, based on diabonas' answer and flying sheep's comment:

\documentclass{article}
\usepackage{tikz}

\newcommand{\contradiction}{%
\begin{tikzpicture}[rotate=45,x=0.5ex,y=0.5ex]
\draw[line width=.2ex] (0,2) -- (3,2) (0,1) -- (3,1) (1,3) -- (1,0) (2,3) -- (2,0);
\end{tikzpicture}
}

\begin{document}

Contradiction? \contradiction

\end{document}

Bear with me, I'm a TikZ newbie. =P

The Unicode symbol "⨳" (U+2A33, it is called "SMASH PRODUCT" for some mysterious reasons) you are looking for is available with modern TeX engines (XeTeX, LuaTeX): You'll have to load the unicode-math package and an appropiate OpenType math font such as XITS Math, then you can access it as \smashtimes.

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{XITS Math}
\begin{document}
    $\smashtimes$
\end{document}

Here's a macro that kludges this symbol out of four \times signs:

\newcommand{\contradiction}{{\hbox{%
    \setbox0=\hbox{$\mkern-3mu\times\mkern-3mu$}%
    \setbox1=\hbox to0pt{\hss$\times$\hss}%
    \copy0\raisebox{0.5\wd0}{\copy1}\raisebox{-0.5\wd0}{\box1}\box0
}}}

This macro requires no additional packages or special fonts; everything it uses is plain vanilla LaTeX.

An explanation of how this works: The second line (beginning with \setbox0) creates a box containing a single \times sign and stores this box in register 0; the \mkern commands add a bit of negative space on either side of the \times so that the left and right sides of the box are flush with the edges of the \times symbol. The next line (beginning with \setbox1) creates a similar box in register 1, except that this box has width 0, with the \times symbol centered horizontally (\hss stands for "horizontal stretch or shrink"; putting it on both sides achieves the centering effect). So here the \times symbol actually extends outside the zero-width box, equally far on both sides. The fourth line copies the contents of the box in register 0 to the output, then copies the contents of the box in register 1 to the output after raising it by half of the width of the box in register 0 (i.e., half of the width of the \times sign), then moves the box in register 1 to the output after lowering it by half of the width of the box in register 0, then moves the box in register 0 to the output.