Change bullet style / formatting in Beamer

You can use

\setbeamertemplate{itemize items}[default]
\setbeamertemplate{enumerate items}[default]

See section 12.1 of the manual of beamer for more information.

\documentclass{beamer}

\usetheme{boadilla}

% Adapted from beamerinnerthemedfault.sty
\setbeamertemplate{itemize item}{\scriptsize\raise1.25pt\hbox{\donotcoloroutermaths$\blacktriangleright$}}
\setbeamertemplate{itemize subitem}{\tiny\raise1.5pt\hbox{\donotcoloroutermaths$\blacktriangleright$}}
\setbeamertemplate{itemize subsubitem}{\tiny\raise1.5pt\hbox{\donotcoloroutermaths$\blacktriangleright$}}
\setbeamertemplate{enumerate item}{\insertenumlabel.}
\setbeamertemplate{enumerate subitem}{\insertenumlabel.\insertsubenumlabel}
\setbeamertemplate{enumerate subsubitem}{\insertenumlabel.\insertsubenumlabel.\insertsubsubenumlabel}
\setbeamertemplate{enumerate mini template}{\insertenumlabel}

\begin{document}

\begin{frame}
\begin{enumerate}
\item{bla}
  \begin{enumerate}
  \item{blubb}
    \begin{enumerate}
    \item{foo}
    \end{enumerate}
  \end{enumerate}
\end{enumerate}
\end{frame}

\end{document}

You can use inner theme constructs to achieve a uniform style. For instance, when I prefer to use square face for items, sections and subsections, I would use the following.

\useinnertheme{rectangles}

Please browse the beamer source code for various themes to get an idea about available inner themes and how various themes define certain styles. I felt that this way was easier to find what I was looking for to customize instead of reading the beamer manual.