Exclude a particular object from the effect of a light source

Is it possible to exclude a particular object from the effect of a light source. Suppose, like point-and-click games, say diablo, where there is a constant spot light at the top of the character, but that light dont cast shadow.

Shadow and lighting are two different things, what do you mean exactly? You can disable shadows with the shadow hint and lights will only work on geometry thats in the same subnode. So if you create two nodes on the rootNode and put the light in the first, all models in the second wont be lit.