Following are the examples of ambident nucleophiles.

1. The resonance forms of acetone enolate.

 The hybrid of the two figures shown above is as follows -

2. The resonance hybrid of thiocyanate ion, ${\text{SCN}}^{-.}$

Both the S and the C atoms can act as nucleophiles.

So, the ${\text{S}}_{\text{N}}2$ reaction of an alkyl halide with ${\text{SCN}}^{-}$ often leads to a mixture of an alkyl thiocyanate and an alkyl isothiocyanate.