Warhawk is an exclusive Playstation 3 combined arms multi-player only game released August 2007(October for Japan) by Incognito and Sony Santa Monica studios. It can be bought in disc form, or downloaded from the Playstation Network. It is the spiritual predecessor of Starhawk. Starhawk is not a direct sequel to Warhawk, despite sharing many similarities.
For more information, visit the Warhawk wiki.