Step 1: Concept
An ambidentate ligand is a monodentate ligand that can coordinate to a metal center through two different atoms.
Step 2: Meaning
Common examples include $CN^-$, $SCN^-$, and $NO_2^-$.
Step 3: Analysis
Nitrite ($NO_2^-$) can bond through the Nitrogen atom (Nitrito-N) or through the Oxygen atom (Nitrito-O).
Step 4: Conclusion
Nitrite is the ambidentate ligand among the options.
Final Answer: (E)