What is the molecular geometry of NHF₂?
You can look up the molecule on chemspider, where you have a little applet for the 3D structure. Or you can download a coordinate file from NIST and view it in a molecular viewer, like Avogadro. Or keep on reading for some deeper insight.

As Klaus already pointed out, if VSEPR is a valid concept, one would arrive at the conclusion, that the molecule is trigonal pyramidal, like ammonia. I performed a DF-BP86/def2-SVP calculation on this to analyse the electronic structure a bit more.
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One reason why VSEPR does fail (a lot) is that lone pairs are more stable in orbitals with high s character. Another point that is often observed is that orbitals with higher p character are directed to more electronegative elements (Bent's Rule).[1,2] As a result of that, the bond angle between electronegative elements gets smaller. This can be observed here, too. From the ideal sp³ arrangement we would expect an 109.5&deg; angle, but here it is about 5&deg; smaller. As a consequence also the hydrogen-nitrogen-fluorine angle has to decrease. In this case the bond angle becomes much smaller because of an intramolecular hydrogen bond.[3]
The NBO analysis consequently builds the same picture:
$$\begin{array}{llll}\hline
\text{type}&amp;\text{main contribution}&amp;\text{other contributions}\\\hline
\sigma\text{-Bd}~\ce{N-F}&amp; 64\%~\ce{F}~(14\% s + 86\% p) &amp; 36\%~\ce{N}~(15\% s + 85\% p) \\
\sigma\text{-Bd}~\ce{N-H}&amp; 68\%~\ce{N}~(25\% s + 75\% p) &amp; 32\%~\ce{H}~(100\% s) \\
\sigma\text{-LP}~\ce{N} &amp; 100\%~\ce{N}~(52\% s + 48\% p) &amp;  \\
\sigma\text{-LP}~\ce{F} &amp; 100\%~\ce{F}~(75\% s + 25\% p) &amp;  \\
\sigma\text{-LP}~\ce{F} &amp; 100\%~\ce{F}~(10\% s + 90\% p) &amp;  \\
\sigma\text{-LP}~\ce{F} &amp; 97\%~\ce{F}~(100\% p) &amp;  2\%~\ce{N}~(7\% s + 93\% p) &amp; 1\%~\ce{F2}~(15\% s + 85\% p)\\\hline
\end{array}$$

The planar (trigonal) structure on this level of theory is about 33 kcal/mol higher in energy. It is the transition state for the nitrogen inversion, which is therefore very slow.



Notes:  


Bent's rule on wikipedia
Bent's rule on our network: Utility of Bent&#39;s Rule - What can Bent&#39;s rule explain that other qualitative considerations cannot?
The bond length is much smaller than the sum of the corresponding van der Waals radii, suggesting a hydrogen bond. Compare A. Bondi J. Phys. Chem., 1964, 68 (3), pp 441–451.
$r_{\mathrm{vdW}}(\ce{HF})=r_{\mathrm{vdW}}(\ce{H})+r_{\mathrm{vdW}}(\ce{F})= (106 + 140)~\mathrm{pm}= 246~\mathrm{pm}$