In case somebody is interested to see how that works for enumerations, i.e., numbered lists, here's the code, adapted from Gonzalo Medina.
\newcounter{copyOfCurrentNumber}
\newcommand{\EnumItem}[1] {%
\begingroup
\setcounter{copyOfCurrentNumber}{\theenumi}
\setcounter{enumi}{#1}
\leavevmode
\usebeamerfont*{enumerate item}%
\usebeamercolor[fg]{enumerate item}%
\usebeamertemplate**{enumerate item}%
\setcounter{enumi}{\thecopyOfCurrentNumber}
\endgroup
}
Now what that code does in addition to replacing itemize by enumerate is to "save" the current enumeration number. So the command \EnumItem receives an argument which equals the number that is supposed to be printed (in the style of the enumerate list of course). But by setting the enumeration number to that of the argument (i.e., the printed number) we change the current enumerate number as a side effect. That is a problem if we are currently within such an enumerate. Thus the code saves the current number in a new variable, and copies it back once the job is done.
Below is the example code plus is visualization.
\begin{frame}[t]{Example}
\begin{enumerate}
\item First list entry.
\item This is label 5: \EnumItem{5} (although we don't have that list entry).
\item Third entry. Still starts with 3, not with 6! Phew!
\end{enumerate}
\end{frame}
