As in my previous thread I mentioned I am running some new wiring for floodlights. I would like to know if I shoud run 12/2 or 12/3 for the lights. They will only be controlled by one switch. If i run the 12/3 for future proofing, can I just put a wire nut on the red conductor at each end of the cable, ie box and fixture?
You can certainly put the extra conductor in and just cap it at both ends.
By "future proofing" do you mean in case you want to add a second switch to control these lights? Depending on how you wire it, you probably will not even need 12/3 between the switch and fixture. You would likely need 12/3 between the two switches, and 12/2 between the switch and the fixture.