sorry to drag this back to the top, but I'm surprised no one mentioned a road flare. I carry road flares. I don't want to be dealing with frustrations of lighting wet wood. Also, it is very likely that most of your rain encounters will also be accompanied by low temperatures. the colder it gets the more your motor skills are affected, first the fine ones followed by the gross ones. the last thing you want to do is fumble around, trying to start a fire, while you're freezing. needless to say, you will have difficulty in handling smaller items, let alone trying to start a fire by some spark based method. Now, I'm an advocate of spark based methods, but a flare is much much much better, if your trying to survive a hypothermic situation.

Alan