Everyone who's a Sonu Nigam fan and everyone who's not (quite a difficult thing to find such a person) will enjoy this.
Especially watch out for his renditions of S. P. Balasubramaniam, Kailash Kher and Adnan Sami songs. Also mimics Anu Malik and Udit Narayan's voices. Simply awesome.
Also look out for his expressions. Priceless.
Thanks to Sujay for pointing out this link.