I'm going to have to go with Bob Baun.
http://www.youtube.com/watch?v=U3yV3ZGXsPY
"April 23, 1964: With the score tied 3-3 late in Game 6 of the Stanley Cup Final at Detroit, Toronto Maple Leafs defenseman Bob Baun took a slap shot on his skate and dropped to the ice in pain. After...