I have heard cattail heads. I have yet to try them in the rain, but since they grow in water i would guess they will be fine. I used one to light a fire and it worked great, it was late summer/fall.

Morning glories. The weed not the flower, they have pods filled with seeds that have a bit of fluff that makes them float on the wind. You have to break up the fluff into a cotton-like tangle. I have been told I am nuts and it does not work, but I have fashioned a torch to light a bonfire with them.