I'm also a fan of the checks sending players all the way back across the ice. If they make it nearly all the way across to the other side, that's cause for an instant replay to verify if they did in fact hit the far boards or not.
Another checking quirk is that sometimes you'll check the player and then continue your speed boost check really far, like from the goal line up until almost centre ice.
If you aim for the top corner from in close and off to the side of the net, but miss the net, the puck will fly off into the sky at a billion miles per hour.
You can one-time the puck out of mid-air.
Sometimes the player will automatically one-time their own rebound (regular slapshot on goal, bounces off the goalie, player automatically makes a huge wind-up and slapshots it again, usually for a goal).
It is possible for two players to check one player at the same time (with the crosscheck animation, into the boards)
Sometimes the goalie spontaneously morphs into a skater and lays a huge crosscheck on an opponent who got too close.
If you check a player and he's relatively near the boards, but another player is between him and the boards, he will still fly into the boards, but from farther than usual.
If you slapshot a puck and hit a player in the head when he's near the boards, he'll fly into the boards violently.
Most of these appear in my old highlights videos
https://www.youtube.com/watch?v=7bMFquzwdFw
https://www.youtube.com/watch?v=RyYwEXRUYE8