The weakest fire based light is the Torch which has a durability and will fall apart with use. The Torch runs down rather quickly but it does allow you the ability to selectively light things on fire (where as a Camp Fire is by chance). This can be a useful strategy for killing large groups of enemies (especially in forests) or for collecting Charcoal.
While it is a light source, it won't warm up your character. It is useful for slowing the rate of freezing. In a pinch, however, the player can light a tree on fire to create a source of warmth which will actually warm the character up. Keep in mind that trees don't usually burn for very long so this is a very innefficient method and should only be used in emergencies.