"Starkiller" is the code name of Galen Marek, Darth Vader's secret apprentice from the Force Unleashed games, however, there are several other instances of the name being used, so you could also mean: Windy Starkiller,a childhood friend of Luke Skywalker.
Starkiller, a Seperatist superweapon.
Gorse Bendak, a Tarisian duelist nicknamed "Bendak Starkiller".
Luke Starkiller, the name of Luke Skywalker in the original draft of The Star Wars.
There are also several other uses of the name.