There's this thing:
http://www.unityjumpstart.com/ProofOfConcept_1/Which teaches you how to make a simple shooter with JS.
And then there's this:
http://forum.unity3d.com/threads/37093-Over-7-hours-of-Unity-Training-Videos-Download-them-nowWhich is based on the above one, but uses C# and goes into more detail.
For a top-down multidirectional shooter there's this:
http://www.rebelplanetcreations.com/downloads/Other/Tutorials/HowToMakeAGameInUnity3D.pdfYou can check the game out here:
http://www.wooglie.com/games/Shooters/EVAC+CITYAnd then there's the tutorial at unity3d.com which uses 3D assets and camera but constraints the gampelay to a 2D plane:
http://unity3d.com/support/resources/tutorials/2d-gameplay-tutorialHowever, all of those are pretty old and may or may not be outdated. Check for youtself.