My take on a gun sinclair build. Focuses on gun for damage and rabbit for utility.
3/13 update: Assistant now has lower base damage and has falloff. Make sure to put the assistant closer to the enemies as the falloff is based on distance to the assistant and not Sinclair.
This change does not really affect gun Sinclair all that much in my opinion and I still am playing him the same way as I have been, but you can focus more on getting up close with Close Quarters/Point Blank instead of Long Range/Sharpshooter if you prefer.