When I was younger I had a hit on a lure, and shortly after it felt like the hook had been spit and hooked on a stump/log. In my younger days I assumed the stronger the line the better, so it was rigged up with 30lb. braided line. After about 10 minutes of pulling and feeling something slowly come to shore, I pulled out a 25 lb. snapping turtle that had almost bit my pickerel in half.
One time in Maine while fishing for pollock (also when I was much younger), I pulled up a longhorned sculpin. I had never heard of or seen anything like it, so it was a little bit surprising.