Two incidents stick out:
1. Long, overnight trip from Virginia to far upstate New York, through the mountains. All manner of critters come out at during the wee hours of the morning. I mowed down a whole family of possums trying to cross the road - an adult and at least 3-4 wee ones. I still feel horrible, but they do look like Satan's minions. I also ran over a large snapping turtle on that trip.
2. About 20 years ago, I hit a bear. Thankfully, I was driving on a winding, curvy country road, in a very small car (Ford Fiesta), so I was probably going 60 km/hr tops. Bashed the hell out of my front end. The bear rolled over onto the shoulder, got up, and just ran off. This was before cell phones, so I definitely didn't want to get out of the car with a really pissed-off bear running around. I sat there for a good half hour before getting out and walking to a nearby farmhouse to call home.
Otherwise, I think I've only hit very small critters - squirrels, a bat, a bird, and moths/insects. Amazingly, no deer, and there are a TON of them around here.