Sparring produced the most injuries, ranging from "turf toe," all the way to some nasty bruises that took a long time to heal.
My worst injury, though, was when I strained a hip flexor after stretching. I felt as if I had gone a wee bit too far while stretching, and stopped. I got up and started walking around the floor, and heard a "pop" sound, and felt the hip seize up. Not nice. Took me several months before I could kick above the waist again, and in all honesty, probably closer to a year and a half before I was pain-free.