Riding in the rain:
If it's really bad weather, I'll run my mountain bike with disc brakes.
-Road bike with frequent feathering (actually, more like semi-permanent)
-Slower speed

-RAT TAIL (saves that dreadful dreadful roadmark from the back of your jeans and shirt)
-front midguard of some sort (saves that roadmark from the front of your shirt
-OR A FULL FENDER SET.
-plastic bag to keep my seat dry when I'm in my destination
-Extra-visible lights
-my snowboard goggles if I'm bombing down a hill (I'll still pull 60 kmhs like an idiot in the rain. Yes, I've been in many accidents. No, I've not learned anything from them.)