This is a debate that is actually going around about the "WYSIWYG" rules versus the new Codexes that have been coming out.. of particular comment is all the new Chaos troops (with exception to the Thousand Sons). Since all the new Chaos troops are supposed to be equipped with Bolter, Bolt Pistol, Close Combat Weapon, Frag Grenades, Krak Grenades, and for Nurgle; Blight Grenades but the models dont physically have the hands or space on them to represent all this gear, how does it affect WYSIWIG??
Heres the so far general consensus of old time gamers and those who arent anti new chaos..
IF it is standard codex wargear and the model does not have anything that is NOT listed then the model is assumed to have all the wargear. In other words a Nurgle marine holding a knife and a bolter is good to represent a Nurgle marine with Bolter, BP, CCW, Frag, Krak, and Blight grenades as long as every other marine is similar. On the other hand the same model would not be acceptable in a squad of supposedly Khornate Berserkers as they do not come with bolters.
IF a model has the options for certain gear that is special to them and is purchased as additional wargear such as a heavy or special weapon, a Vet Sgt getting a Power fist, or a Chaos Lord getting a Daemon weapon; then he/she/it should be modeled with it. And similarly if the model has the weapon then you better have paid the points for him to have it as we again dont want to think that you have a model with a power fist only to find out he had nothign special on him.
In short if they have special gear then we want to see it and if we see it they better have it. Hope that makes sence.