Skylift
The Skylift is a very large heavy-lift helicopter featured in Grand Theft Auto IV's The Ballad of Gay Tony DLC. It resembles a S-64 Skycrane/Aircrane. It is not normally driveable or obtainable; and is only seen in two missions, both for Yusuf Amir.
The Skylift is however, obtainable with a minor exploit involving stopping yusuf at the skylift mission, killing yusuf and claiming the skylift.