Great first post Icarus.
Keg, I have to disagree with you regarding "tiredness" as being something worth briefing. Go to the Flight Safety Foundation and take a look at their ALAR tool kit.
http://www.mtc.gob.pe/portal/transpo...df/fsf_rat.pdf
Being tired might not be the result of turning up to work tired. Long duty periods mean you may feel much different at the end of a long day/night. Complacency and the effects of fatigue are risk factors that can be worth highlighting. If a guy mentions Terrain as a risk, I am sure you could use the same arguement of "what should we do differently". I think challenging a guy for raising a risk may be more counterproductive than hearing him out.