In a moment, someone else will likely be along with a better idea, but you might try combining geometrical symbols from the ifsym package with other symbols with /rlap or /llap. E.g., the following works so-so, though you'd likely need to tweak it for the font and fontsize you're using, and other spacing needs:
Code: Select all
\documentclass{article}
\usepackage[geometry]{ifsym}
\newcommand{\bigexclaim}{\raisebox{-0.1em}{\BigTriangleUp}\hspace{-0.32em}\llap{\small\textbf{!}}\hspace{0.32em}}
\begin{document}
Wow\bigexclaim ~That's cool.
\end{document}
I think there are simpler solutions from some of the graphical packages like pstricks and/or tikz, but I'm too lazy to look right now.
P.S. Ok, I'm not as lazy I thought. With pstricks you could use something like \newcommand{\bigexclaim}{\pstribox{\Large\textbf{!}}} -- I've been trying to avoid pstricks lately myself because of the hassle of not being able to use pdflatex directly, however, though latex > DVI > PS > PDF works.