Two words,
Ayrton Senna. He was king in the rain.
Watch this video of the opening lap of Donnington. He came from a fourth place start to first in less than one lap. Amazing!! He used to push his lead times racing in drizzle and light rain on slicks while all the others came in for intermediate or rain tires.
http://youtube.com/watch?v=fVQFEFtFBCA
Just as a reference, watch this Senna video from his McLaren days:
http://www.youtube.com/watch?v=QbHGB3NNlsQ