What do you think about the following (requires the verbatim package):
\newcommand{\zzTop}{\vspace{-2\parskip}}
\newcommand{\zzBot}{\vspace{-1\parskip}}
\newenvironment{tightverbatim}
{\zzTop\verbatim}
{\endverbatim\zzBot}
I'm also thinking about putting a -1\parskip between theorems and proofs.