\documentclass{article}

\usepackage{pgfplots}
\usepackage{german}
\usepackage[utf8]{inputenc} % erlaubt direkte Nutzung von Umlauten
\pgfplotsset{compat=1.9}

% \usetikzlibrary{}
% \usepgfplotslibrary{}

\begin{document}

\begin{tikzpicture}
	\begin{axis}[
		symbolic x coords={Ä,B$x \pm 2$,&,\&},
		xtick=data,
		xticklabel={\ifnum\ticknum=2 (and)\else \tick\fi},
	]
	\addplot coordinates {(Ä,2) (B$x \pm 2$,3) (&,4) (\&,5)};	
	\node[draw] at (axis cs:&,2.5) {$(2,2.5$};
	\end{axis}
\end{tikzpicture}

\begin{tikzpicture}
	\begin{axis}[
		symbolic x coords={Ä,B$x \pm 2$},
		xtick=data,
		xmin={[normalized]-2},
		extra x ticks={{[normalized]-1.5}},
	]
	\addplot+[error bars/.cd,
		x dir=plus,x explicit]
	coordinates {(Ä,2) +- (1,0) (B$x \pm 2$,3)};	

	\node[draw] at (axis cs:{[normalized]1},2.5) {$(1,2.5$};
	\end{axis}
\end{tikzpicture}
\end{document}

