Adidas raingear. The pants are fine but a bit warm. I find the large jacket too small and XL too large.
Worst rain -- we have a tournament called the hard day's scramble. It's in December, just before Christmas. We use it to collect toys for the underprivileged kids in the neighborhood. The local police collect the toys and give them to the kids. They usually have to rent a few U-Haul trucks. Anyway, this one year, it rained torrents. High winds. You couldn't see the ball on the tee, and it wouldn't stay still in the fairway or on the green. The holes on the greens were full of water -- one hole was cut on a low part of the green, and was surrounded by a 6' wide puddle of water that you had to putt through.
I did finish my round, as did most others.