I have a waterproof jacket and full-zip rain pants. They fit up into two tiny balls in my backpack when I don't need them. I can take them on and off quickly, without taking off my shoes/boots, so my commute isn't any worse for it. Bone dry at the end of my ride.
In Austin, the rain tends to come in torrents, so there's no such thing as riding in a drizzle... if I feel a drop, by the time I get to my destination I'll be absolutely drenched no matter what, so the rain gear is my only rain riding getup. I don't even have fenders on my daily commuter since rain is so rare here; my only fendered bike has steel rims. If I'm on my cruiser, I wait out the rain.